Making Plastic Greener Through Next Generation Polymers

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“Making Plastic Greener Through Next Generation Polymers”

Dr. Joseph Fortunak Professor of Chemistry, Howard University

Dr. Marc Hillmyer Director Center for Sustainable Polymers, University of Minnesota


www.acswebinars.org This ACS Webinar is co-produced with the ACS Green Chemistry Institute

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Polymers are produced on the teragram scale.

1

The U.S. plastics industry creates nearly $400 billion in annual shipments.

2

Polymer production is largely based on finite feedstocks.

3

Polymer waste persists in the environment.

4

Making Plastic Greener  Through Next Generation Polymers Kechun Zhang

Frank  Bates

Marc A. Hillmyer

!

C&E News June 2, 2014

Mingyong Xiong

Debbie  Schneiderman 5

Susan Freinkel “In a world of nearly seven billion souls and counting, we are not going to feed, clothe and house ourselves solely from wood, ore and stone; we need plastics. And in an era when we’re concerned about our carbon footprint, we can appreciate that lightweight plastics take less energy to produce and transport than many other materials. Plastics also make possible green technology like solar panels and lighter cars and planes that burn less fuel. These “unnatural” synthetics, intelligently deployed, could turn out be nature’s best ally.” New York Times 17 March 2011

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Photographer Sarah Leen

From “The end of cheap oil” National Geographic June 2004

lightweight

moldable

protective

insulating

strong

disposable

transparent

Giant Molecules Time Life Books

1966

7

inexpensive 8

What could the future polymer industry look like? Biomass (waste or non-nutritive ) bio, organic, & inorganic chemists Monomers (new and established ) polymer chemists & materials scientists Sophisticated materials (structure-controlled) all stakeholders Sensible end-of-life solutions (recycling, incineration, compost) integrated efforts by chemists, chemical engineers & materials scientists

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Downloaded from Downloaded from www.sciencemag.org on May 15, www.sciencemag.org 2013

on May 15,

2 2 51. S. to Krohns et al., Nat. Mater. 10, 899 (2011). 40. SOS Metals Inc., personal communication. et al., Environ. Sci. Technol. 42, 6446 (2008). essential amino acids, with no 31. E. Williams 1,4-diaminobutane (Fig. 3) H 52. C. F. Izard, D. B. Muller, Resour. Conserv. Recycling 54, 41. A. King, Nat. Mater. 10, 162 (2011). 32. I. Oswald, A. Reller, Gaia 20, 41 (2011). NH2 2 real value for food or feed, as 33. X. Chi, M. Streicher-Porte, M. Y. NH (52), the starting material for H2NCONH H2O 1436 (2010). 42. C. Hagelüken, C. W. Corti, Gold Bull. 43, 209 (2010). L. Wang, M. A. Reuter, 2 L-arginine 53. K. Nakajima et al., Environ. Sci. Technol. 44, 5594 (2010). 43. R. Kahhat, E. Williams, Environ. Sci. Technol. 43, 6010 (2009). Manag. 31, 731 (2011). L-ornithine chemical feedstocks. This would 34. J.Waste Nylon-4,6. 54. T. Hiraki et al., Sci. Technol. Adv. Mater. 12, 035003 (2011). 44. A. Sepulveda et al., Environ. Impact Assess. Rev. 30, Huisman et al., 2008 Review of Directive 2002/96 on again circumvent the fuel-versus- Waste Electrical and Electronic Equipment (WEEE) There is a great here for 55. K. Nakajima, O. Takeda, T. Miki, K.need Matsubae, T. Nagasaka, 28 (2010). Environ. Sci. Technol. 45, 4929 (2011). 45. H. Tabuchi, “Japan Recycles Minerals from Used (United University, Bonn, Germany, 2007). Fig. Nations 3. 1,4-Diaminobutane from cyanophycin. food issue. out-of-the-box thinking. Chem56. G. Gaustad, E. Olivetti, R. Kirchain, J. Ind. Ecol. 14, 286 (2010). Electronics,” New York Times, 4 October 2010. 35. P. Chancerel, S. Rotter, Waste Manag. 29, 2336 (2009). 57. M.ists Fuse, are E. Yamasue, B. K. Reck, T. E. Ecol. Econ. 46. Honda, “Honda to reuse rare earth metals contained in Another, potentially enor- 36. M. Oguchi, S. Murakami, H. Sakanakura, A. Kida, accustomed toGraedel, thinking 70, 788 (2011). used parts,” 17 April 2012; http://world.honda.com/news/ T. Kameya, Waste Manag. 31, 2150 (2011). mous source of protein waste 37. European proteinogenic amino 58. A. of van Schaik, M. A. Reuter, Miner. Eng. 23, acids 192 (2010). 2012/c120417Reuse-Rare-Earth-Metals/index.html. Commission, Critical Raw Materials for the EU. 59. A. vanmolecules Schaik, M. A. Reuter, Miner.are Eng. synthe20, 875 (2007). 47. Chancerel, C. recovery E. M. Meskers,and C. Hagelüken, Rotter, Report of the on Definingviability Critical er Group economic by P.enabling that could be exploited in the future will beAd-hoc the Working as S.largely chiral that J. Ind. Ecol. 13, 791 (2009). Raw Materials (DG Enterprise and Industry, Brussels, 2010). reuse of(2008). the enzyme. Furthermore, by-products from the production biofuels. It JOM sized from Acknowledgments: simple starting materials. they The authors thank theNow anonymous 48. J. G. Johansson,immobilization A. E. Bjorklund, J. Ind. Ecol. 14, 258 (2010). 38. of M. Reuter, A. van Schaik, 60, 39 reviewers for their constructive 49. M. Oguchi, H. Sakanakura, A. Terazono, Takigami,to start 39. term, T. G. Gutowski, in Thermodynamics the Destruction wouldandsuppress degradation of the protease by H.have is generally agreed that, in the long this will thinking about comments. how to convert Waste Manag. 32, 96 (2012). of Resources, B. R. Bakshi, T. G. Gutowski, D. Sekulic, Eds. autolysis largely involve second-generation biofuels from these same 10.1126/science.1217501 amino acids back to relatively sim50. T. Minami, Thin Solid Films 516, 5822 (2008). (Cambridge Univ. Press, Cambridge, 2011),(49). pp. 113–132. In the second stage, individual amino acids ple commodity chemicals in an economically lignocellulosic biomass and nonedible triglycerides. It has been estimated (48) that if 10% of must be isolated from the protein hydrolysate. viable manner. An illustrative example is proerated in increasingwhich quantities themade biodiesel transportation fuels, currently derived from fossil Standard methods generally involve fractiona- vided by L-phenylalanine, canbybe REVIEW industry and could become a “waste.” By applyfeedstocks, were substituted by biomass-derived tion on the basis of physicochemical charac- by enzymatic addition ammoniaanalysis, to cinnaming even a crudeofvalorization one finds fuels, this could generate 100 Mt/year of protein teristics such as molecular size, charge, and ic acid. However, the of fermentative producthat conversion glycerol to the chemical epi-enormous Waste constitutes an chlorohydrin is economically attractive compared worldwide. This amount is of the same order of hydrophobicity. Here, there is a clear need for tion of L-phenyalanine from biomass has potential resource:  the alternatives, because theeconomical value of this conmagnitude as the protein requirement of the innovation. Certain amino acids could perhaps become so to efficient that the most version is 3 times that of conversion to transporworld population. In an integrated biorefinery, be selectively converted—by enzyme-catalyzed way to produce cinnamic acidthat is of probably of megatonnes (Mt)/year tationhundreds fuel and 10 times burning tofrom generate 2 1 Tuck,1 Eduardo Pérez,1 István T. * Roger A.products Sheldon,3*that Martyn LPoliakoff * electricity—hence decarboxylation, forHorváth, example—to these proteins could form a Christopher source ofO.bulk -phenylalanine by the reverse reaction. One Solvay’s recentthe commissionacross world. ing of a new 100,000 epichlorohydrin plant chemicals via a three-stage process: (i) isolation can be more easily separated. In one approach, can also imagine that, at at/year certain feedstock the carbon-based compounds currently manufactured by waste the chemical derived basedefficient on glycerol in Thailand (7). In the longer an amino acid–rich from industry po- are and hydrolysis of the proteinsMost to of mixtures of protamylase, price and with technology, integration from petroleum. The rising cost and dwindling supply of oil have been focusing attention on term, glycerol could become molecule 11a platform tato starch fuels, processing, wasfrom usedbiomass as a feedstock amino acids, (ii) separation ofpossible the individual the deamination decarboxylkg or but 10the14 g) (10fine routes to making chemicals, and solvents instead. In this of context, leading towith manysubsequent different chemicals, forassessed the pilot-scale ofdifferent ethanoldedicated and crops amino acids, and (iii) conversion ofrecent the amino ation could afford a bio-based styrene many studies have the relative coproduction merits of applying establishment of suchprocess platformsfor will require a to chemical production. Here, we highlight the opportunities diverting existing residual (CGP: a nitrogenfor storage polymer acids into bulk organic compounds, which will cyanophycin (Fig. 4). much more mature bio-based chemical industry. biomass—the by-products of present agricultural and food-processing streams—to this end. Most biomass waste is a complex and vargenerally comprise large-volume industrial iable mixture of molecules, and separation bemonomers. imes are rapidly changing. Who could particularly via conversion to chemicals. How- comes a key issue. An added complication is A promising technology for the isolation of that in 2012 a commercialever, making a commercial case for such a process have imagined O O that some of both the bio-waste and the materials must necessarily include the cost of replacing the ly viable venture would involve shipping to be separated are solid; therefore, separation proteins from biomass residues involves so-called ~200,000 tonnes (t)/year of household waste OHoriginal function frequently involves organic solvents. If bio-based PAL of the waste—for example, OH ammonia fiber expansion (AFEX) pretreatment from Italy to Rotterdam for use as a feedstock for powering the mills with hydroelectricity. Indeed, chemical production is to become self-sustaining, whereby cellulose is separatedelectricity from proteins NH 2 one can quantify the value of different “waste those solvents must also be bio-based and cangeneration in Dutch power plants with that are solubilized. The protein fraction(1)?can overcapacity Waste is lucrative business or, valorization” strategies (Table 1). Cinnamic acid not, in the long term, be derived from crude oil. L-phenylalanine Styrene Because the sources of waste are so diverse, it In addition, bio-based solvents would be highly as they in northern England: “Where there’s then be hydrolyzed. Traditionally, thissayinvolved PALto=consider L-phenylalanine ammonia the chemistry in termslyaseuseful materials in their own right. If such solmuck there’s brass.” Since the early 1990s, atten- is convenient prolonged treatment with concentrated mineral tion has been diverted from waste remediation to of four source-independent categories: polysac- vents can also function as fuel additives and platacids at elevated temperatures,waste leading evenlignin, triglycerides fats and oils), form chemicals, one would have the basis for a prevention, with the emphasis on applying charides, Fig. 4. L-Phenylalanine to cinnamic acid and(from styrene. tually to the formation of copious amounts of chemistry” (prevention is and proteins. As explained later, lignin is chal- genuinely robust technology (8). the principles of “green to breakfermentation down into chemically useful better than (2). Now the focus is moving lenging Some of the processing of petrochemical hyinorganic salts as waste. A milder andcure) more from of biomass toward exploiting environmentally attractive alternative involvesthose wastes that are largely fragments. By contrast, pretreatment of poly- drocarbon feedstocks involves the introduction saccharides, triglycerides, and proteins can lead of oxygen-containing functional groups by, for unavoidable. by yeast the use of proteases, such as the In alkaline pro- produced in vivo by cyanobacteria) building Glutamic acid, the most abundant, nonblocks: monosacits most general sense, the term “waste” to their constituentTuck etofal. Science 2012 10 fermentation (Fig. 3) (50). CGP consists a tease alcalase, which is widely covers used in laundry essential amino acid derived from the hydrolysis any organic material apart from the pri- charides, fatty acids plus glycerol, and amino acids, Table 1. Approximate valorization of biomass several recent of specialized materialinfor the plants were origdetergents. It has been used, formary example, thewhichpoly( many plant and L-aspartic acid) respectively. backbone There with are equimolar waste foranimal differentproteins, uses* (48,can 58). be conon the conversion of biomass toverted chemicals grownshrimp (e.g., cornamounts stover from or reviews hydrolysis of proteins in poultry inally (46) and to a variety of commodity chemicals via of maize L-arginine side chains and, because lignin from paper pulping). Nearly all wastes (3–6). However, exploiting waste in a profitable Value ($/t biomass) waste (47). A possible drawbackcurrently of thishave method it is insoluble under physiological conditions, initial decarboxylation catalyzed by glutamic acid some value—for instance, stover way is a highly multidisciplinary problem; therebulkHowever, chemical not all the1000 is the relatively high cost of theforenzymes. Ima-decarboxylase (53). routes beoreasily isolated the fermentation we outline here recent developments for a Average improving the soil in it thecan fields, lignin as a fore,from Transportation fuel 200–400 optimizing fuelprovide to powergreatpaper mills. Here, we concentrate wider audience with the emphasis on are mobilization of the protease could sustainable. A life-cycle assessment study (54) broth. Cattle feed† 70–200

Valorization of Biomass: Deriving More Value from Waste

T

on ways of getting higher value from the waste,

698

1

University of Nottingham, Nottingham NG7 2RD, UK. 2City AUGUST 2012 VOL Hong 337 University 10 of Hong Kong, Tat Chee Avenue, Kowloon, Kong. 3Delft University of Technology, Delft, Netherlands. *To whom correspondence should be addressed. E-mail: [email protected] (M.P.), istvan.t.horvath@cityu. edu.hk (I.T.H.), [email protected] (R.A.S.)

the valorization of the various components of Generating electricity 60–150 residual biomass. Cost Waste is perhapswww.sciencemag.org a concept even broader than SCIENCE –400 the definition above, because it applies to any Landfill biomass-derived by-product for which supply *Taken from (48) apart from data for cattle feed. The values are based on costs in the Netherlands, but the order of the values is greatly exceeds demand. For example, glycerol likely to be similar across the developed world. †Data from (58); can be a valuable chemical, but it is being gen- this range of values depends on the quality of the feed.

How many billion kilograms in one teragram? www.sciencemag.org

SCIENCE

VOL 337

695

10 AUGUST 2012

(a)1 (b)10 (c)100 (d)1000

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Center for Sustainable Polymers NSF Center for Chemical Innovation

• Established at UMN in May 2009 • Phase I NSF CCI September 2011 • Phase II CCI from the NSF August 2014

@UMN_CSP

Managing  Director

Director of  EO&D

Laura  Seifert

Jennifer  Henderson

Frank Bates

Michelle  Chang

Geoff Coates

Chris  Cramer

Will  Dichtel

John  Hartwig

Marc  Hillmyer

Tom  Hoye

Anne  LaPointe

Chris Macosko

Mark  Matsen

Theresa Reineke

Bill  Tolman

Dean  Toste

Jane  Wissinger

Kechun  Zhang

csp.umn.edu

12

CSP Grand Challenge Discover efficient and precision conversions of renewable raw materials into innovative polymeric products that outperform the current suite of non-sustainable polymers from performance, environmental, and cost perspectives.

13

Integrative elements • Center management Streamlined & lean approach that fosters creativity • Innovation Effective engagement and partnerships with industry • Education and Professional Development Train tomorrow’s leaders in sustainable science and technology • Informal Science Communication Capture the attention of kids and adults on a grand scale • Broadening Participation Actively encourage diversity as a critical ingredient for success 14

[email protected]

612-625-7834

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Next Generation Feedstocks thrust OH

O

O

HO HO

OH

OH

HO

O

O

OH

Controlled Polymerization Processes thrust

O O

d,l-lactide O Hybrid Polymer Structures thrust

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lactic acid

O HO

lactide

O

– H2O

polylactide

O

O

O

OH

catalyst

O

O

O O

n

• Compost: 100% in ~45 days

sugar

• Incinerate: Low residue • Recycle: Chemical and mechanical • Cost ~ PS and PETE • Toughness & thermal limitations (Tg ≈ 60 °C) • 100’s of millions of kilograms per year

Most market forecasts: ~20% annual growth rate in bioplastics

Tg: high

low

17

high

Marriage of elastomers and plastics: thermoplastic elastomers

Nexar www.kraton.com

global market > 1.5 x 109 kg

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Letter pubs.acs.org/macroletters

Sustainable Thermoplastic Elastomers from Terpene-Derived Monomers Justin M. Bolton,† Marc A. Hillmyer,* and Thomas R. Hoye* Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States S Supporting Information *

pinenes

ABSTRACT: ABA triblock polymers were prepared by living anionic polymerization of the pinene-derivable monomers αmethyl-p-methylstyrene and myrcene. The resulting thermoplastic elastomers displayed microphase separation at moderate molar mass, an upper service temperature about 70 °C higher than traditional petroleum-derived styrenic thermoplastic elastomers, competitive tensile strengths of up to 10 MPa, impressive ultimate elongations of up to 1300%, and remarkably low energy loss recovery attributes.

T

sequential anionic

block-poly(α-methylene-γ-butyrolactone) triblocks exhibit a noticeably improved upper service temperature due to the high Tg (≈195 °C) of their hard blocks.10 These TPEs also show impressive ultimate elongations (>1800%) and continued performance at elevated temperatures where styrenic TPEs lose strength. With the aim of developing new, high-performing, and sustainable TPEs, we explored the use of terpenes as a naturally occurring feedstock. Both limonene and myrcene are derivable by pyrolysis of β-pinene, a major constituent of turpentine.11−13 Limonene can be dehydrogenated to yield α-methyl-pmethylstyrene (AMMS, 1, Figure 1),14 a compound that has

hermoplastic elastomers (TPEs) are used in wide ranging applications including personal care products, pressuresensitive adhesives, footwear, asphalt, and coatings. Since the 1960s, styrenic triblock polymer-based TPEs such as poly(styrene)-block-poly(butadiene)-block-poly(styrene) (or SBS) have been a mainstay in the consumer market.1 Over 1.7 billion kilograms of SBS and related poly(isoprene)-based TPEs are forecasted for production in 2017.2 TPEs have properties similar to cross-linked rubbers, yet they can be melt-processed as thermoplastics. This is because the high glass transition temperature (Tg) poly(styrene) (PS, Tg ≈ 100 °C) end blocks that flank the low Tg poly(butadiene) (PB, Tg ≈ −80 °C) midblocks microphase segregate and act as physical cross-links that reinforce the rubbery matrix. This yields a strong elastomeric material that has a service temperature range dictated by the Tgs of the PS and PB segments. Contemporary styrenic triblock polymers are derived from finite oil-based feedstocks and thus belong to the large family of petrochemicals that are inspiring efforts to shift toward sustainable alternatives.3,4 Moreover, the Tg of PS limits the upper service temperatures, because the physical cross-links weaken when the hard domains soften. One strategy for extending the service temperature of styrenic TPEs is to substitute the PS blocks with a higher Tg polymer such as poly(α-methylstyrene) (PMS, Tg = 172 °C)5 or poly[(cyclohexyl)ethylene] (PCHE, Tg = 147 °C).6 However, neither PMS nor PCHE are renewably sourced. Advances toward sustainable TPEs have begun to emerge. One example is an all polyester-based triblock comprising poly(lactide) hard blocks and a poly(methyl caprolactone) elastomeric midblock.7 Although these triblocks possess excellent mechanical properties, they suffer from thermal as well as hydrolytic instability and, correspondingly, reduced upper service temperatures and lifetimes.8,9 All-renewable poly(α-methylene-γ-butyrolactone)-block-poly(menthide)© XXXX American Chemical Society

myrcene

polymerization

Si

sBu

α-methyl4-methylstyrene

sBu

thermoplastic elastomer

ACS Macro Lett. 2014, 3, 717.

19

Figure 1. Structures of the monomers α-methyl-p-methylstyrene (1) and myrcene (2) and of a derived triblock copolymer 3. 15,16

only rarely been polymerized. Myrcene (2) is a 2substituted-1,3-butadiene that previously has been incorporated [as poly(myrcene) (PMYR)] as the rubbery midblock in a styrenic TPE that showed promising mechanical properties.17,18 We hypothesized that an ABA triblock such as 3, having high Tg poly(AMMS) (PAMMS) end blocks flanking a PMYR central block, has potential value as a sustainable TPE. Received: June 6, 2014 Accepted: July 3, 2014

717

dx.doi.org/10.1021/mz500339h | ACS Macro Lett. 2014, 3, 717−720

Article pubs.acs.org/accounts

Aliphatic Polyester Block Polymers: Renewable, Degradable, and Sustainable Marc A. Hillmyer* and William B. Tolman* Department of Chemistry and Center for Sustainable Polymers, University of Minnesota, 207 Pleasant Street Southeast, Minneapolis, Minnesota 55455, United States CONSPECTUS: Nearly all polymers are derived from nonrenewable fossil resources, and their disposal at their end of use presents significant environmental problems. Nonetheless, polymers are ubiquitous, key components in myriad technologies and are simply indispensible for modern society. An important overarching goal in contemporary polymer research is to develop sustainable alternatives to “petro-polymers” that have competitive performance properties and price, are derived from renewable resources, and may be easily and safely recycled or degraded. Aliphatic polyesters are particularly attractive targets that may be prepared in highly controlled fashion by ring-opening polymerization of bioderived lactones. However, property profiles of polyesters derived from single monomers (homopolymers) can limit their applications, thus demanding alternative strategies. One such strategy is to link distinct polymeric segments in an A−B−A fashion, with A and B chosen to be thermodynamically incompatible so that they can self-organize on a nanometerlength scale and adopt morphologies that endow them with tunable properties. For example, such triblock copolymers can be useful as thermoplastic elastomers, in pressure sensitive adhesive formulations, and as toughening modifiers. Inspired by the tremendous utility of petroleum-derived styrenic triblock copolymers, we aimed to develop syntheses and understand the structure−property profiles of sustainable alternatives, focusing on all renewable and all readily degradable aliphatic polyester triblocks as targets. Building upon oxidation chemistry reported more than a century ago, a constituent of the peppermint plant, (−)-menthol, was converted to the ε-caprolactone derivative menthide. Using a diol initiator and controlled catalysis, menthide was polymerized to yield a low glass transition temperature telechelic polymer (PM) that was then further functionalized using the biomass-derived monomer lactide (LA) to yield fully renewable PLA−PM−PLA triblock copolymers. These new materials were microphase-separated and could be fashioned as high-performing thermoplastic elastomers, with properties comparable to commercial styrenic triblock copolymers. Examination of their hydrolytic degradation (pH 7.4, 37 °C) revealed retention of properties over a significant period, indicating potential utility in biomedical devices. Acc. In addition, they were to be useful in pressure-sensitive adhesives formulations and Chem. Res.shown 2014, 47, 2390. as nucleating agents for crystallization of commercially relevant PLA. More recently, new triblocks have been prepared through variation of each of the segments. The natural product α-methylene-γbutyrolactone (MBL) was used to prepare triblocks with poly(α-methylene-γ-butyrolactone) (PMBL) end blocks, PMBL−PM− PMBL. These materials exibited impressive mechanical properties that were largely retained at 100 °C, thus offering application advantages over triblock copolymers comprising poly(styrene) end blocks. In addition, replacements for PM were explored, including the polymer derived from 6-methyl caprolactone (MCL). In sum, success in the synthesis of fully renewable and degradable ABA triblock copolymers with useful properties was realized. This approach has great promise for the development of new, sustainable polymeric materials as viable alternatives to nonrenewable petroleum-derived polymers in numerous applications.

■

BACKGROUND AND CONTEXT

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criminate disposal of polymers after their (often brief) use can be severe. In the long term, current paradigms for the generation and disposal of polymers are simply unsustainable. The key to shifting to sustainable alternatives will be to prepare both existing and new low-cost polymers with competitive performance properties from renewable feedstocks. In addition, to address the end-of-life issue, we must also develop polymers that can be more easily recycled, autonomously degraded to

Polymers, the molecules of plastic, are predominantly derived from fossil feedstocks and are annually produced on the teragram scale. They are inexpensive, in general, and are remarkably useful; lightweight, durable, protective, conductive, and self-healing are just a few of the many attributes of modern polymers that render them critical in countless technologies. Yet, such polymers are “challenged” with respect to sustainability. The Earth harbors finite carbon-based feedstocks that are being rapidly depleted by our increasing energy demand. Moreover, environmental impacts from the indis-

What is the approximate glass transition temperature of PLA? © XXXX American Chemical Society

Received: March 13, 2014

A

dx.doi.org/10.1021/ar500121d | Acc. Chem. Res. XXXX, XXX, XXX−XXX

(a) –60 °C (b) 0 °C (c) 60 °C (d) 160 °C

21

arrhizus, R. delemar, Pseudomonas sp. and Candida cylindracea. In particular, the lipases from R. arrhizus and R. delemar proved to be very effective in promoting hydrolysis.

(Keywords: biodegradable copolyester; methylvalerolactone-lactide; hydrolysis)

INTRODUCTION The extensive use of bioresistant synthetic polymers is considered to be one cause of environmental pollution. The current demand for easy disposal of polymers has instigated many investigations on the synthesis and evaluation of novel biodegradable polymers. These polymers are expected to find applications in medicine (sutures, implants), pharmacy (drug release) and agriculture (mulch, food packaging) 1. Although several polymers have been identified as degradable in model aqueous media or in animal bodies, the family of aliphatic polyesters appears at the moment to be the most attractive and promising z 5. A long methylene chain promotes biodegradability by imparting flexibility to the polymeric chain. Therefore, poly(6-valerolactone) and poly(e-caprolactone), with four and five methylene units, respectively, in their backbones, are more biodegradable than poly(fl-propiolactone), with two methylene units 6. However, a much longer methylene chain might cause a decrease in biodegradabilitf because of a decrease in the density of ester bonds in the main chain. Furthermore, substituent groups were also found to decrease the susceptibility of polymers to biodegradation 6. To the best of our knowledge, poly(De-fl-methyl-6valerolactone) (poly(MV)) has not been reported except for its oligomer as a raw material of polyurethane. Poly(MV) is expected to be biodegradable, and the interest for its current study lies in its structure, valeric acid found in the valerian plant which reflects two antagonistic tendencies with regard

to biodegradability: the methylene chain promotes biodegradability, whereas the methyl pendent group has an adverse effect upon the susceptibility of a polymer to degradation. On the other hand, L-lactide (LA) is a well known monomer used extensively for the synthesis ofbioabsorbable polymers for biomedical applications 8-16. Since poly(LA) has a rigid macromolecular structure, various approaches to increase its flexibility have been devised, among which its copolymerization with other monomers is a promising one. Copolyesters 8'17-19, copoly(ester ether)s 2°-24 and • Org. Syn. 1955, 35, 87 are the polymer families that copoly(ester amide)s 11"25 have been more thoroughly investigated. The copolymer of• e-caprolactone and flavor LA hasinbeen repeatedly studied by Spicy-apple, sweet Turkish tobacco  several researchers (Tobac. Sci. 1973,because 18, 43) of its appealing mechanical properties 9.26-2 9. The aim of this investigation is to synthesize by • Cyclic ester susceptible to ROTEP ring-opening polymerization (Scheme 1) novel copolyesters combining the attractive features of MV (flexibility) and • ROTEP produces aand low Tg LA (hydrolysability) to polyester study their thermal and mechanical properties and biodegradability.

β-methyl-δ-valerolactone

O

α

H3C

O

δ

β

γ

• Early German & Japanese polymer patents (PUs)

EXPERIMENTAL

• Extensive literature on use as synthon Reagents DL-fl-Methyl-6-valerolactone (Kuraray) was purified little in under the literature polymers (Boehringer, by• Very distillation vacuum.onL-Lactide

(Valeriana officinalis)

+

o

•

o

* To w h o m correspondence should be addressed

Scheme 1

Synthesis and degradability of a novel aliphatic polyester…

22

Nakayama et al. Polymer 1995, 6, 1295. POLYMER Volume 36 N u m b e r 6 1995

1295

Mevalonate final titer = 88 g L–1

Semisynthesis:  High yielding dehydration  & hydrogenation Direct  βMδVL  biosynthesis (i) overexpression of the mevalonate-producing enzymes (ii) introduction of the fungal siderophore proteins to  synthesize anhydromevalonolactone (AML) (iii) reduction of AML to βMδVL by enolate reductases

23

O HO R OH +

Triazabicyclodecene

O

TriazaTBD bicyclodecene H 20 °C, bulk

O O

O O n/2

R

H O

O n/2

(±)-βMδVL Temperature (°C)

[βMδVL]/[TBD]/[BnOH]=492/1/1.7

140 120 100

80

60

40 30 20 10 5 0

ΔHp = −14 kJ mol–1  ΔSp = −46 J mol−1K−1

2.0 80

60

40

20

5

3

50

75 80

0.5

85

2 1

0.0 0

0

70

1.0

4

ln[M]eq

ln[([M]0-[M]eq)/([M]-[M]eq)]

60

50

100 Time (min)

100 Time (min)

150

Conversion (%)

Monomer Conversion (%)

1.5

10 20 30 40 50

90

-0.5 95

150

2.4

2.6

2.8

3.0

3.2 -1

3.4 3.6x10-3

1/T (K )

91% conversion at RT within a few hours using 0.05 wt% triazabicyclodecene

24

Triazabicyclodecene TBD

O HO R OH +

O

O O O

20 °C, bulk

O

O O

evealed no evidence of significant βMδVL) and poly(lactide) blocks, the desired ABA triblock archi-

rity of poly(lactide) and poly P(L)LA triblock polymers readily erate molar masses as evidenced try (DSC) and small-angle X-ray βMδVL)–PLA [from (±)-lactide, A [from (-)-lactide, LLA] exhibit midblock and endblock segments the SAXS data from these tritering peaks that correspond to with principal spacings ranging Table S8). nd thermal properties of these uenced by molar mass, tacticity d composition. By changing the onent (fLA = 0.29) to the majority ble to access either elastomers or ed composition and molar mass, endblocks leads to remarkably ercially available petroleum based coverability, tensile strength, and able S9) (23).

O

O n/2

O m/2

R

O O n/2

R

O

O

O OH

HO

O O

O

n/2 O O Conclusion We have developed a semisynthetic approach to βMδVL from P(L)LA-P(βMδVL)-P(L)LA glucose that relies upon the fermentation of mevalonate and subsequent transformation of mevalonate to βMδVL. The high titer of the fermentation (88 g L−1) and the efficiency of the chemical reactions used to produce the final product make the overall process scalable and commercially promising. We also have described a nonnatural total biosynthetic pathway for the production of βMδVL , which obviates the need for additional chemical transformations. Optimization of this all-biosynthetic process (i.e., titer and yield comparable to the semisynthetic route) would further reduce the production cost of βMδVL. This bioderived monomer can be readily converted from the neat state to a rubbery hydroxytelechelic polymer using controlled polymerization techniques at ambient temperature; addition of either (±) NMR or SEC (-)-lactide to a poly(βMδVL) midblocks leads to well-defined ABA triblock polymers. We have shown that the thermal and mechanical properties of these materials can be tuned by controlling molar mass, architecture, and endblock tacticity and have specifically demonstrated thermoplastic elastomers with properties similar to commercially available styrenic block polymers. This work lays the foundation for the production of new biobased polymeric materials with a wide range of potential properties and applications.

H O m/2

O O O (±) or (–)-lactide

Triaza(TBD) bicyclodecene

20 °C, DCM

25

DSC

26

SAXS D

Well-organized lamellar morphology  at moderate molar masses

hromatography traces obtained from PLA–PβMδVL–PLA PβMδVL (20.0 kg mol−1) (16.2–20.0–16.2 and a correspondingkg PLLA–PβMδVL–PLLA (9.1–20.0–9.1 mol−1)  −1 R spectra obtained from (Bottom) PβMδVL, (Middle) PLLA (10.0 mol ), and (Top) PLLA–PβMδVL–PLLA (9.1–20.0–9.1 (D =kg33 nm) rded for (Bottom) PβMδVL and (Middle) PLA–PβMδVL–PLA (16.2–20.0–16.2 kg mol−1), and (Top) PLLA–PβMδVL–PLLA en while heating at a rate of 5 °C min−1 after cooling from 200 °C at the same rate. (D) SAXS pattern recorded at room 16.2–20.0–16.2 kg mol−1). Diffraction peaks at q*=0.185 nm−1, 2q*, 3q*, and 4q* are consistent with a periodic (d =

nas.1404596111

H+ n/2

HO–P(βMδVL)–OH

(±)-βMδVL

H

O

H

Xiong et al.

27

was 0.26 g/g glucose. To prepare anhydromevalonolactone we added sulfuric acid directly to the fermentation broth and heated to reflux to catalyze the dehydration of mevalonate (Fig. 2E and Fig. S1). At a catalyst loading of 10% by volume, 98% of the mevalonate was converted to anhydromevalonolactone with a selectivity of 89% (Table S6). The resulting anhydromevalonolactone was isolated by solvent extraction using chloroform and hydrogenated to βMδVL using Pd/C as the catalyst (bulk, room temperature, 350 psi H2, 12 h) to >99% conversion. The crude product was subsequently purified by distillation to obtain polymerization-grade monomer (Fig. 2F).

107 kg mol–1

Polymerization of βMδVL. Based on previous work with alkyl-

substituted δ-valerolactones, we suspected the ceiling temperature for the polymerization of βMδVL might be low (28, 37, 38). To favor high conversion we therefore conducted the polymerizations in bulk monomer at room temperature using the highly Fig. 1. (A) Total biosynthetic pathway for the production of βMδVL. (B) A active organocatalyst triazabicyclodecene (TBD) (Fig. 3) (39). The semisynthetic route to produce βMδVL from mevalonate. (C) Conversion of 28 Fig. 5. (A)βMδVL Representative (σ) versus strain (e) results obtainedthat in uniaxial extension for triblock polymers containing differentof volume fractions of addition TBD to neat βMδVL in the presence of benzyl alcohol to anstress elastomeric triblock polymer can be repeatedly stretched emicrystalline (f ) and glassy (f ) blocks. Incorporation of relatively small amounts of the hard block (f = 0.29 and f = 0.32) results in a soft (elastic to1.918 itsrespectively), original length without breaking. (BnOH) as(Ethe modulus E = andtimes 5.9 MPa, highly extendable elastic material. Increasing the hard block content (f = 0.59) leads to a stiff = 229initiator MPA) and ([βMδVL]0/[TBD]0/[BnOH]0 = 492/1/1.7) LLA

LA

LA

−1

LLA

LA

ductile plastic. (B) Stress versus strain response of PLLA–PβMδVL–PLLA (18.6–70.0–18.6 kg mol ) (fLLA = 0.32) during cyclic loading (1–20 cycles) to 67% strain at a rate of 5 mm min−1. These results demonstrate nearly ideal elastic behavior with nearly complete recovery of the applied strain.

8358 | www.pnas.org/cgi/doi/10.1073/pnas.1404596111

Plasmids and Strains. All cloning procedures were carried out in the E. coli train XL10-gold (Stratagene). Genes for mevalonate and βMδVL pathway were either PCR amplified from genomic DNA templates or codon-optimized and synthesized by GenScript. Three kinds of plasmids have been constructed for the biosynthesis of βMδVL (Fig. S4). BW25113 (rrnBT14 ΔlacZWJ16 hsdR514 ΔaraBADAH33 ΔrhaBADLD78) transformed with the relevant plasmids was used to produce mevalonate or βMδVL.

Culture Condition and Analysis. E. coli strains were growth at 37 °C in 2XYT ich medium (16 g/L Bacto-tryptone, 10 g/L yeast extract, and 5 g/L NaCl) supplemented with appropriate antibiotics (ampicillin 100 μg/mL and kanamycin 50 μg/mL). Shake flask fermentations were performed with 125-mL conical flasks containing M9 medium. After adding 0.1 mM isopropyl-β-D-thiogalactoside, the ermentation was performed for 48 h at 30 °C. Scale-up fermentation was performed in 1.3 L Bioflo 115 Fermentor (NBS). The culturing condition was 500concentrations liter scale up onof5 et at 34 °C, dissolved oxygen level 20%, and pH 7.0. The metabolites were measured by HPLC.

Polymer Synthesis. To synthesize poly(βMδVL) a monofunctional (benzyl alcohol) or difunctional (1,4 benzene dimethanol) alcohol was added to monomer in a pressure vessel or glass vial and stirred with a magnetic stir bar until completely dissolved. The ratio of monomer to alcohol was varied to target polymers of different molecular weights. When the initiator was dissolved, an appropriate amount of catalyst (∼0.05–0.2 mol% TBD or ∼0.5 mol% diphenyl phosphate) relative to monomer was added to initiate the polymerization. The reaction was stirred and the conversion monitored using 1H NMR of crude quenched aliquots. Poly((L)LA)-b-poly(βMδVL)-b-poly ((L)LA) was prepared from a previously isolated and purified poly(βMδVL). The poly(βMδVL) prepolymer was first dissolved in a 1 M solution of (±)lactide or (–)-lactide in dichloromethane. After dissolution of the prepolymer, 0.1 mol% TBD (relative to lactide) was added. The solution was stirred for 10 min and then quenched by adding 5 equivalents of benzoic acid relative to TBD. The crude polymer samples were purified by precipitation in 29 March 2014 methanol from dichloromethane/chloroform and subsequently dried.

ACKNOWLEDGMENTS. D.K.S. thanks Byeongdu Lee for assistance with Dehydration, Hydrogenation, and Purification. The fermentation supernatant acquisition of SAXS data, and Justin Bolton for photography assistance. was treated with concentrated H2SO4 to dehydrate mevalonate into anhyFunding for this work was provided by the Center for Sustainable Polymers dromevalonolactone. The reaction temperature was 121 °C. Chloroform was at the University of Minnesota, a National Science Foundation (NSF)-supported Center for Chemical Innovation (CHE-1136607). The BioTechnology Institute used to extract anhydromevalonolactone from the reaction mixture. The at the University of Minnesota is also acknowledged for support. Portions esults of dehydration are shown in Fig. S1 and Table S6. For hydrogenation, of this work were performed at Sector 12-IDB of the Advanced Photon unreduced palladium on activated carbon [10% (wt/wt) Acros Organics] was Discover efficient and precision10conversions ofwere renewable Source (APS). Use of the APS, an Office of Science User Facility operated used as the catalyst. In a typical hydrogenation procedure, g of catalyst for the US Department of Energy (DOE) Office of Science by Argonne raw materials into innovative polymeric products that added to a 300 mL high-pressure reactor with 50 mL anhydromevalonolactone. National Laboratory, was supported by the US DOE under Contract DEoutperform the current suite of non-sustainable polymers The reaction was then allowed to stir under H2 (∼350 pounds per square inch from performance, environmental, and cost perspectives.AC02-06CH11357. Additional parts of this work were carried out in the gauge) at room temperature overnight to ensure quantitative conversion. University of Minnesota College of Science and Engineering CharacterizaThe crude βMδVL was dried over calcium hydride for 12 h and then distilled tion Facility, which receives partial support from NSF through the National Next Generation thrust dry Nanotechnology Infrastructure Network program. under vacuum (50 mTorr, 30 °C); the distilled product was Feedstocks passed through C&E News June 2, 2014

OH O O OH 1. Miller SA (2013) Sustainable polymers: Opportunities for the next decade. ACS Macro 8. Yim HO HOH, et al. (2011) Metabolic engineering of Escherichia coli for direct production of O HO Lett 2(6):550–554. 1,4-butanediol. Nat Chem Biol 7(7):445–452. O OH OH 2. Atsumi S, Hanai T, Liao JC (2008) Non-fermentative pathways for synthesis of branched9. Tseng HC, Prather KL (2012) Controlled biosynthesis of odd-chain fuels and chemicals Controlled Polymerization chain higher alcohols as biofuels. Nature 451(7174):86–89. via engineered modular Ometabolic pathways. Proc Natl Acad Sci USA 109(44): Processes thrust 3. Xu P, et al. (2013) Modular optimization of multi-gene pathways for fatty acids O 17925–17930. production in E. coli. Nat Commun 4:1409. 10. Achkar J, Xian M, Zhao H, Frost JW (2005) Biosynthesis of phloroglucinol. J Am Chem O d,l-lactide 4. Dellomonaco C, Clomburg JM, Miller EN, Gonzalez R (2011) Engineered reversal of Soc 127(15):5332–5333. Structures the β-oxidation cycle for the synthesis of fuels and chemicals. Hybrid NaturePolymer 476(7360): 11.thrust Causey TB, Zhou S, Shanmugam KT, Ingram LO (2003) Engineering the metabolism of Escherichia coli W3110 for the conversion of sugar to redox-neutral and oxidized 355–359. 5. Bastian S, et al. (2011) Engineered ketol-acid reductoisomerase alcohol deXiong et and al. Proc. Natl. Acad. Sci. 2014, 111, 8357. products: homoacetate production. Proc 30 Natl Acad Sci USA 100(3):825–832. 12. Park SJ, et al. (2013) Metabolic engineering of Escherichia coli for the production of hydrogenase enable anaerobic 2-methylpropan-1-ol production at theoretical yield in 5-aminovalerate and glutarate as C5 platform chemicals. Metab Eng 16:42–47. Escherichia coli. Metab Eng 13(3):345–352. 13. Ajikumar PK, et al. (2010) Isoprenoid pathway optimization for Taxol precursor 6. Steen EJ, et al. (2010) Microbial production of fatty-acid-derived fuels and chemicals overproduction in Escherichia coli. Science 330(6000):70–74. from plant biomass. Nature 463(7280):559–562. 14. Ma SM, et al. (2009) Complete reconstitution of a highly reducing iterative polyketide 7. Enquist-Newman M, et al. (2014) Efficient ethanol production from brown macrosynthase. Science 326(5952):589–592. algae sugars by a synthetic yeast platform. Nature 505(7482):239–243.

Xiong et al.

PNAS | June 10, 2014 | vol. 111 | no. 23 | 8361

CHEMISTRY

For details, see SI Appendix.

Xiong et al.

basic alumina using cyclohexane as an eluent. The cyclohexane was removed under vacuum to obtain purified βMδVL.

APPLIED BIOLOGICAL SCIENCES

Materials and Methods

How much does Prof. Hillmyer love sustainable polymers? (a) not at all (b) somewhat This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.

(c) a lot Communication

(d) a little too much pubs.acs.org/JACS

ne succinate): A New Polymer Stereocomplex

ela M. DiCiccio, and Geoffrey W. Coates*

31

and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States

ion

biotechnology.10 In contrast, polyesters synthesized via the ring-opening alternating copolymerization (ROAC) of epoxides and cyclic anhydrides can be made by purely chemical means with a wide array of commercially available starting materials. A variety of metal-based complexes have been reported to is an open access article published under an ACS AuthorChoice License, which permits catalyze this reaction.6 We recently discovered that This cobalt copying and redistribution of the article or any adaptations for non-commercial purposes. salcy complexes (salcy = N,N′-bis(salicylidene)cyclohexanediimine) with a nucleophilic cocatalyst such as Communication + [PPN][NO3] ([PPN] = [Ph3P −NPPh3]) can be used for pubs.acs.org/JACS the regioselective ROAC of various cyclic anhydrides and epoxides (Scheme 1a).6m

we show the formation of a polymer ng isotactic, regioregular chains of te) synthesized via the copolymerdrides and epoxides. The stereocantly improved thermal properties enantiopure parent polymers. We ocomplexation is a route to a new polyesters with improved properdily accessible starting materials.

Poly(propylene succinate): A New Polymer Stereocomplex

ctic polypropylene are the two most ymers in the world, accounting for mately 100 million pounds of plastic the United States alone.1 These are ubiquitous because of their low cal and thermal properties, allowing ay of applications. Since the discovery ely few new classes of semicrystalline mercialized, and even fewer where the readily available and inexpensive as One potential class includes polymers tactic versions of which were first same time as the first isotactic efins, epoxides are inexpensive and them attractive monomers for largeer, unlike simple α-olefins, their contain stereogenic centers, which a challenge for synthesizing polymers

ABSTRACT: Herein we show the formation of a polymer stereocomplex by mixing isotactic, regioregular chains of poly(propylene succinate) synthesized via the copolymerization of cyclic anhydrides and epoxides. The stereocomplex exhibits significantly improved thermal properties in comparison to the enantiopure parent polymers. We demonstrate that stereocomplexation is a route to a new class of semicrystalline polyesters with improved properties, produced from readily accessible starting materials.

biotechnology.10 In contrast, polyesters synthesized via the ring-opening alternating copolymerization (ROAC) of epoxides and cyclic anhydrides can be made by purely chemical means with a wide array of commercially available starting materials. A variety of metal-based complexes have been reported to catalyze this reaction.6 We recently discovered that cobalt “It is relevant to the world of industrial polymers because it salcy complexes (salcy = N,N′-bis(salicylidene)cyclohexanediimine) with a nucleophilic cocatalyst such as renewable raw addresses issues with biodegradation, [PPN][NO3] ([PPN] = [Ph3P+−NPPh3]) can be used for and the demands placedand on modern plastics. In this thematerials, regioselective ROAC of various cyclic anhydrides epoxides case,(Scheme that 1a). is 6m the ability to crystallize quickly from the melt

C&E News November 17, 2014

olyethylene and isotactic polypropylene are the two most and1.have a melting point above 100 °C. In principle, this Scheme (a) Regioselective Polymerization of Cyclic widely produced polymers in the world, accounting for Anhydrides and Epoxides (b) aStereocomplex discovery couldandbe keystoneFormation of a new line of thermoplastic over half of the approximately 100 million pounds of plastic by Crystallization of Enantiomeric Polymer Chains produced annually in the United States alone.1 These polymers.” - Eric P. Wasserman, Dow Chemical semicrystalline polyolefins are ubiquitous because of their low cost and impressive physical and thermal properties, allowing for their use in a wide array of applications. Since the discovery of these materials, relatively few new classes of semicrystalline JACS spotlight polymers have been commercialized, and even fewer where the monomers are nearly as readily available and inexpensive as J. Am. Chem. Soc. 2014, 136, 15807−15808 ethylene and propylene.2 One potential class includes polymers made from epoxides, isotactic versions of which were first synthesized around the same time as the first isotactic 3 polyolefins. As with olefins, epoxides are inexpensive and readily available,copolymerization making themChem. attractive Soc. monomers for largeCatalytic epoxide/anhydride not2014, only 32 J. Am. 136, 15897. (ACS Editors’ Choice) scale polymers. However, unlike simple α-olefins, their utilizes a large substrate scope, but alsocontain allows control over corresponding epoxides stereogenic centers, which can be Additionally, both an asset and a challenge for synthesizing polymers polymer microstructure. by employing the controlled tacticity.4 regioselective ROAC ofofEpoxides enantiopure with copolymerizacyclic have also beenepoxides studied in alternating 5 with CO2 tocan formbepolycarbonates and which with cyclic anhydrides, highly tactictionspolyesters synthesized, anhydrides to form polyesters. 6 In the case of the increases the probability for crystallinity in the Catalytic epoxide/anhydride copolymerization not only copolymerization of propylene oxide (PO) resulting with CO2, even utilizes a large substrate scope, but also allows control over highly regio- are and stereoregular poly(propylene carbonate) materials. Because thesethepolyesters chiral, using enantiopure polymer microstructure. Additionally, by employing the is amorphous.7 However, we hypothesized that the copolyepoxides results in enantiomerically pure forms of each regioselective ROAC of enantiopure epoxides with cyclic merization of PO with cyclic anhydrides could result in the anhydrides, highly tactic polyesters can be synthesized, which Article Online formation chains of a new class semicrystalline given the polymer. When these handed areofmixed, theypolyesters can result View increases the probability for crystallinity in the resulting wide array of anhydride comonomers available. In general, View Journal | View Issue in an amorphous mixture, a semicrystalline material with materials. Because these polyesters are chiral, using enantiopure polyesters are functionally diverse and bioresponsive, giving epoxides results in enantiomerically pure forms of each segregated homocrystallites, or a semicrystalline with to them advantages over polyolefins in the material range of applications 8 polymer. When these handed chains are mixed, they can result which they can be applied. Additionally, many commercial stereocomplexed crystallites (Scheme 1b). Although we have in an amorphous mixture, a semicrystalline material with aliphatic polyesters, including polylactic acid (PLA), polyhysegregated homocrystallites, or a semicrystalline material with observed many examples of the former two situations,(PCL), we are droxybutyrate (PHB), and polycaprolactone can be stereocomplexed crystallites (Scheme 1b). Although we have decomposed in aerobic composting environments, and in vivo 9 observed many examples of the former two situations, we are in the case of biomedical devices. However, commercializing View Article Online ofCOMMUNICATION the current biodegradable polyesters for large-scale use Received: September 12,many 2014 Cite this: Chem. Commun., 2015, challenges the existing industrial infrastructure because the Received: September 12, 2014 View Journal | View Issue Published: 2014 required to produce them rely partially or fully on Published: November 4, 2014 51, 2731 November 4, processes

P

ChemComm

COMMUNICATION

15897

Olefins ChemComm

from biomass feedstocks: catalytic ester decarbonylation and tandem Heck-type coupling†

Published on 12 January 2015. Downloaded by University of Minnesota - Twin Cities on 02/03/2015 20:52:12.

© 2014 American Chemical Society

S Supporting Information *

Published on 12 January 2015. Downloaded by University of Minnesota - Twin Cities on 02/03/2015 20:52:12.

n studied in alternating copolymerizam polycarbonates5 and with cyclic olyesters. 6 In the case of the pylene oxide (PO) with CO2, even eoregular poly(propylene carbonate) we hypothesized that the copolyyclic anhydrides could result in the of semicrystalline polyesters given the comonomers available. In general, y diverse and bioresponsive, giving yolefins in the range of applications to ed.8 Additionally, many commercial ding polylactic acid (PLA), polyhynd polycaprolactone (PCL), can be omposting environments, and in vivo devices.9 However, commercializing gradable polyesters for large-scale use ndustrial infrastructure because the duce them rely partially or fully on

Scheme 1. (a) Regioselective Polymerization of Cyclic Julie M. Longo, Angela M. DiCiccio, and Geoffrey W. Coates* Anhydrides and Epoxides and (b) Stereocomplex Formation Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States by Crystallization of Enantiomeric Polymer Chains

Alex John, Levi T. Hogan, Marc A. Hillmyer* and William B. Tolman*

Olefins from biomass feedstocks: catalytic © 2014 American Chemical Society 15897 dx.doi.org/10.1021/ja509440g | J. Am. Chem.ester Soc. 2014, 136, 15897−15900 Received 11th November 2014, dx.doi.org/10.1021/ja509440g | J. Am. Chem. Soc. 2014, 136, 15897−15900 decarbonylation and tandem Heck-type coupling† Accepted 3rd January 2015 DOI: 10.1039/c4cc09003a www.rsc.org/chemcomm

Cite this: Chem. Commun., 2015, 51, 2731

Alex John, Levi T. Hogan, Marc A. Hillmyer* and William B. Tolman*

Received 11th November 2014, Accepted 3rd January 2015 DOI: 10.1039/c4cc09003a www.rsc.org/chemcomm

With the goal of avoiding the need for anhydride additives, the catalytic With the goal of avoiding the need for anhydride additives, the catalytic decarbonylation of p-nitrophenylesters aliphatic carboxylic acids decarbonylation of p-nitrophenylesters of aliphaticofcarboxylic acids

to their corresponding olefins, including commodity monomers like

to their corresponding olefins, including monomers likeby styrene and acrylates, hascommodity been developed. The reaction is catalyzed

palladium complexes in the absence of added is ligands and is promoted styrene and acrylates, has been developed. The reaction catalyzed by by alkali/alkaline-earth metal halides. Combination of catalytic decar-

palladium complexes in thebonylation absence addedcoupling ligands is promoted and of Heck-type with and aryl esters in a single pot

process demonstrates the viability of employing a carboxylic acid as by alkali/alkaline-earth metal halides. Combination of catalytic decara ‘‘masked olefin’’ in synthetic processes.

bonylation and Heck-type coupling with aryl esters in a single pot

Biomass, and chemicals derived therefrom, hold promise in transi-

process demonstrates the tioning viability of employing a carboxylic acid acids as to a more sustainable bio-based economy.1 Carboxylic are an important class of biomass-derived molecules that can be a ‘‘masked olefin’’ in synthetic processes. used as starting materials for the synthesis of a variety of potentially useful compounds. For example, polymerizable olefins may be

accessed through transition metal catalyzed dehydrative decarbonyBiomass, and chemicals derived therefrom, hold promise in transilation of aliphatic carboxylic acids (Fig. 1, top).2–4 Such reactions 1 2d often employ Pd,3,4 Rh or Ir5 catalysts and phosphine based tioning to a more sustainable bio-based economy. Carboxylic acids ligands, with some recent attention to use of base metals like Fe6 are an important class ofandbiomass-derived molecules that canreported be Ni.7 An indispensable ingredient in all of the processes is a synthesis sacrificial stoichiometric anhydride, acetic (Ac2O) or used as starting materials thus forfar the of a variety oflike potentially pivalic anhydride (Piv2O), which activates the carboxylic acid subuseful compounds. For strate example, polymerizable olefins may be by forming a mixed anhydride that can readily undergo oxidative addition to the metal center. A key goal of current research Chem. Commun. accessed through transition metal catalyzed dehydrative decarbonyis to increase the efficiency of the reaction and avoid the use of such 2–4 a stoichiometric (and wasteful) co-reagent. Whilereactions some success lation of aliphatic carboxylic acids (Fig. 1, top). Such in effecting5 decarbonylation of carboxylic acids directly at high often employ Pd,3,4 Rh2dtemperatures or Ir (200–250 catalysts and phosphine based 1C) using Ru catalysts has been reported,8 of high yields of under mildmetals conditionslike appears ligands, with some recentattainment attention to use base Fe6to require activation of the acid. and Ni.7 An indispensable ingredient in all of the processes reported thus far is a sacrificial stoichiometric anhydride, like acetic (Ac2O) or Department of Chemistry and Center for Sustainable Polymers, University of Minnesota, 207 Pleasant St SE, Minneapolis, MN, 55455-0431, USA. pivalic anhydride (Piv2O), which activates the carboxylic acid subE-mail: [email protected], [email protected]; Fax: +1-(612)-626-8659; Tel: +1-(612)-625-4061 strate by forming a mixed anhydride that can readily undergo † Electronic supplementary information (ESI) available: Experimental procedures, characterization and NMR spectra compoundsresearch synthesized and oxidative addition to the metal center. Adatakey goal of for current isolated. See DOI: 10.1039/c4cc09003a is to increase the efficiency of the reaction and avoid the use of such a stoichiometric (and wasteful) co-reagent. While some success This journal is © The Royal Society of Chemistry 2015 in effecting decarbonylation of carboxylic acids directly at high temperatures (200–250 1C) using Ru catalysts has been reported,8 attainment of high yields under mild conditions appears to require activation of the acid.

Department of Chemistry and Center for Sustainable Polymers, University of Minnesota, 207 Pleasant St SE, Minneapolis, MN, 55455-0431, USA. E-mail: [email protected], [email protected]; Fax: +1-(612)-626-8659;

Fig. 1 Comparison of previous work to decarbonylation and in situ Hecktype coupling reactions reported herein.

Herein, we report (a) the development of a palladium-catalyzed decarbonylation of p-nitrophenylesters of aliphatic carboxylic acids to the corresponding olefins, and (b) demonstration of the viability Fig. 1 Comparison previous work to from decarbonylation and in situ Heckof a one-pot tandem Heck-typeofcoupling reaction starting the p-nitrophenylesters hydrocinnamicreported acid (a styrene precursor) and type couplingof reactions herein. the p-nitrophenylesters of various aromatic carboxylic acids (Fig. 1, bottom). The catalytic decarbonylation of p-nitrophenylesters differs from the typical decarbonylation that involves intermediacy of a mixed anhydride. The tandem Heck-type process is particularly notable, especially we in light of recent(a) efforts biomass of a palladium-catalyzed Herein, report theto incorporate development derived chemicals in synthesis,9 and because Heck-coupling is a decarbonylation of p-nitrophenylesters of aliphatic carboxylic acids powerful synthetic tool for coupling alkenes with aromatics.10 earlycorresponding precedent for the use olefins, of esters as substrates toAnthe and (b)includes demonstration of the viability the demonstration of a Ni(0)-mediated decarbonylation of phenyl of a one-pot tandem coupling propionates to yield ethylene usingHeck-type simple phosphine ligands likereaction starting from the PPh3 and PCy3.11 It was also noted in this work that (i) more than p-nitrophenylesters of hydrocinnamic acid (a styrene precursor) and one turnover could be achieved with esters of electron-withdrawing the p-nitrophenylesters ofsimple various aromatic phenols like p-cyanophenol and (ii) that alkyl esters did not carboxylic acids (Fig. 1, participate in the reaction. We were also inspired by the report of bottom). The catalytic decarbonylation of p-nitrophenylesters differs a palladium-catalyzed decarbonylation of p-nitrophenylesters of aromatic acids, which in the presence of alkenes resulted from carboxylic the typical decarbonylation that involves intermediacy of a in a Heck-type coupling via a putative aryl–Pd intermediate.12

2015, 51, 2731.

mixed anhydride. The tandem Heck-type process is particularly notable, especially in light of recent efforts to incorporate biomass Chem. Commun., 2015, 51, 2731--2733 | 2731 derived chemicals in synthesis,9 and because Heck-coupling is a powerful synthetic tool for coupling alkenes with aromatics.10 An early precedent for the use of esters as substrates includes the demonstration of a Ni(0)-mediated decarbonylation of phenyl propionates to yield ethylene using simple phosphine ligands like PPh3 and PCy3.11 It was also noted in this work that (i) more than one turnover could be achieved with esters of electron-withdrawing phenols like p-cyanophenol and (ii) that simple alkyl esters did not

33

Poly(acetylated methacrylic isosorbide) [PAMI] tds00 | ACSJCA | JCA10.0.1465/W Unicode | research.3f (R3.6.i7:4236 | 2.0 alpha 39) 2014/12/19 13:33:00 | PROD-JCAVA | rq_4446580 |

2/26/2015 15:49:28 | 6 | JCA-DEFAULT

James J. Gallagher, Marc Research A. ArticleHillmyer,* and Theresa M. Reineke* pubs.acs.org/journal/ascecg Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455 1

Isosorbide-based Polymethacrylates

2

James J. Gallagher, Marc A. Hillmyer,* and Theresa M. Reineke*

3

Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States

4

S Supporting Information *

5

ABSTRACT: A new monomer, acetylated methacrylic isosorbide (AMI), was synthesized in two steps employing scandium(III) triflate as a remarkably efficacious catalyst for the tandem esterification of isosorbide with acetic anhydride and methacrylic anhydride. Analysis of the crude product mixture after acetylation indicated that functionalization occurred preferentially at the endo hydroxyl group of isosorbide (endo-acetate:exo-acetate = 4.2:1). Reaction of this mixture with methacrylic anhydride gave the corresponding isomeric mixture of AMI monomers. Poly(AMI) [PAMI] prepared by radical polymerization of the mixture of AMI regioisomers was found to have a high glass transition temperature (Tg ≈ 130 °C) and good thermal stability (Td, 5% weight loss; N2 = 251 °C, air = 217 °C). Reversible addition−fragmentation chain transfer (RAFT) polymerization of AMI using a new chain transfer agent, hydroxyethyl 4-cyano-4-(phenylcarbonothioylthio)pentanoate (HO-CPAD), yielded PAMI-CTA samples with controlled molar masses and narrow molar mass distributions (Đ ≤ 1.09). Subsequent chain extension of PAMI-CTA with n-butyl acrylate gave a series of PAMI-b-PnBA block copolymers ranging from 17−36 wt % PAMI. All samples of PAMI-b-PnBA exhibited two well-separated Tg values at approximately −45 and +120 °C, indicative of microphase separation. KEYWORDS: Renewable, polymer, high Tg, RAFT, block copolymer, scandium(III) triflate, butyl acrylate

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INTRODUCTION

solubility and Tg of poly(VDT)s. Polymers prepared from monomer with the vinyl triazole group in the endo position had a Tg ≈ 71 °C and were water-soluble, whereas those prepared from monomer with the vinyl triazole in the exo position had a Tg ≈ 118 °C and were insoluble in water. The authors noted that the RAFT polymerization of VDTs required about 48 h to reach 50−70% conversion, presumably due to the bulky nature of VDT monomers and modest reactivity of the N-vinyl triazole moiety. Various options for functionalizing the hydroxyl groups of isosorbide have been reported in the literature (e.g., esterification, etherification, carbonylation, tosylation).4 Due to the relatively poor reactivity of the secondary alcohols, esterification methods typically employ the use of auxiliary reactants. For example, a routine procedure for acetylating isosorbide uses acetic acid, N,N-dicylcohexylcarbodiimide, and catalytic 4-dimethylaminopyridine (i.e., Steglich esterification).16,17 Acetylation by this method occurs predominantly at the less sterically encumbered exo position (∼60% of product mixture) due to the steric bulk of the O-acyl isourea intermediate (for structure of isosorbide, see Scheme 1). An alternative approach for acetylation uses acetic anhydride and catalytic lead(II) oxide (∼2 mol % relative to isosorbide).18−21 This method favors acetylation at the endo position (∼80% isolated yield). Although more sterically hindered due to being

Renewable chemical feedstocks are becoming increasingly cost competitive with petroleum based analogs as a result of advances in synthetic methods and production processes. For example, recent improvements in the conversion of the glucose derivative sorbitol to isosorbide have made the latter a viable building block for biobased polymers on the commercial scale.1,2 Often compared to bisphenol A due to its rigid bicyclic structure and diol functionality, isosorbide has been incorporated into a wide variety of step growth polymers, including polyesters, polycarbonates, polyethers, polyurethanes, and polytriazoles.3−5 These polymers generally exhibit high glass transition temperatures (Tg) due to the rigid bicyclic structure of isosorbide. Additionally, various difunctional derivatives of isosorbide have been employed in the synthesis of cross-linked, thermoset polymers for use in high performance composites.6−11 Despite the numerous examples of isosorbide-based polymers, there are only a few examples of monovinyl isosorbide derivatives for use in linear chain growth polymerizations.12−15 A monovinyl isosorbide monomer is an appealing building block because the construction of polymers with designed architectures is more easily accomplished via chain growth mechanisms. Beghdadi et al. have described the synthesis and reversible addition−fragmentation chain transfer (RAFT) polymerization of isosorbide derived vinyl dianhydrohexitol triazoles (VDTs).12 Interestingly, the authors found that the placement of the vinyl triazole moiety at either the endo or exo position of isosorbide had a significant effect on the © XXXX American Chemical Society

Thermally stable,  high glass transition temperature polymethacrylate from sugar. (isosorbide comes from the hydrogenation & dehydration of glucose) 52 53 54 55 56 57 58 59

ACS Sustainable Chem. Eng. in press 2015 (ACS Editors’ Choice)

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Received: December 23, 2014 Revised: February 10, 2015

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DOI: 10.1021/sc5008362 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

Discover efficient and precision conversions of renewable raw materials into innovative polymeric products that outperform the current suite of non-sustainable polymers from performance, environmental, and cost perspectives. Next Generation Feedstocks thrust

C&E News June 2, 2014

OH HO HO

O

O O OH OH

OH

HO

O Controlled Polymerization Processes thrust

O O

d,l-lactide O Hybrid Polymer Structures thrust Xiong et al. Proc. Natl. Acad. Sci. 2014, 111, 8357.

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Making Plastic Greener Through Next Generation Polymers

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