Simultaneous Interpenetrating Network Materials Derived from

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10 Simultaneous Interpenetrating Network Materials Derived from Reaction of Organostannane Dihalides With Lignin and Hydroxyl-Capped Poly(ethylene oxide) and ABA Block Copolymers Charles E . Carraher, Jr. , Dorothy C. Sterling , Thomas H. Ridgway , William Reiff , and Bhoomin Pandya 1

3

1

2

1

Department of Chemistry, Florida Atlantic University, Boca Raton, FL 33431 Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221 Mössbauer Spectroscopy Consultants, Burlington, M A 01803

1 2

3

Simultaneous interpenetrating network materials have been formed from the interfacial polycondensation of organotin halides with lignin and hydroxyl-capped poly(ethylene oxide) and ABA block copolymers where A is polyethylene glycol and Β is poly(dimethylsiloxane). Struc tural characterization includes Fourier transform infrared spec troscopy, Mössbauer spectroscopy, elemental analysis, and electron ionization mass spectroscopy. Ion fragments that contain moieties from the organotin, lignin, and hydroxyl-capped coreactants are found.

L l I G N I N RANKS SECOND ONLY TO SACCHARIDES AS A NATURAL, renewing material. Lignin is produced at an annual rate of about 2 X 1 0 tons and is present in the biosphere in over 10 times this amount. Lignin is produced in mills at an annual rate of about 5 Χ 10 tons (1-3). Only about 2 % of this lignin is isolated for further use; the remainder is discarded or burned as fuel. Lignin sulfonates are the most widely employed industrial surfactant (1), and they also have been reacted with a number of agents to take advantage of low 10

7

0065-2393/94/0239-0221306.00/0 © 1994 American Chemical Society

Klempner et al.; Interpenetrating Polymer Networks Advances in Chemistry; American Chemical Society: Washington, DC, 1994.


222

INTERPENETRATING POLYMER NETWORKS

cost and high availability to produce feedstock. Lignin has been incorporated into phenol-formaldehyde resins (4-6) and reacted with isocyanates (7-12), alkene oxides (13-16), and epichlorohydrin-forming epoxy resins (17, 18). Even so, lignin remains a largely underused material. We recently reported on the reaction between lignin and organostannane halides (19). As expected, products derived from reaction with dihalides were cross-linked, whereas products derived from monohalides were not. The products were "brick dustlike" in nature and showed no flexibility. This lack of flexibility was due to the rigid nature of the phenol groups present in the lignin and connected through hydrogen bonding. These products are de picted in structure 1 for materials derived from trialkyltin halides. The present chapter reports attempts to produce flexible products by employing flexibilizing groups. Flexibility groups typically include methylene, ethylene oxide, and siloxane moieties (20). To increase the flexibility of lignin, hydroxyl-capped polyethylene glycol and hydroxyl-capped block copolymers of poly(ethylene oxide-co-dim ethylsiloxane-co-ethylene oxide) were investigated as potential flexibilizing agents. The emphasis in this chapter is on structural results.

Experimental Details Chemicals. Chemicals were used as received. Indulin AT, which is a purified (typically greater than 99%) form of lignin obtained from the krafting process, was a gift From Westva Company (Charleston, SC). The hydroxyl-capped compounds were all obtained from Petrarch (Briston, PA) and the organostan nane dichlorides were obtained from Aldrich (Milwaukee, WI). The percentage

Ç C

Structure 1. Portion of lignin product from reaction with dialkyltin chlorides.


10.

CARRAHER ET AL.

223

SIN Materials

of hydroxyl present in the lignin was determined by use of a modification of the procedure given in reference 21. The modifications are reported in reference 19. Analysis showed that the employed lignin had 1.14-mequiv/g phenolic hydroxyl and 8% catechol and other aromatic hydroxyls. The remainder of the lignin content was aliphatic hydroxyls with a total hydroxyl content of 3.30-mequiv/g or 59 hydroxyls for every 100 C units. The employed lignin had a weight-average molecular weight of 3500 Da and a number-average molecular weight of 1600 Da. Structure 1 has a molecular weight of about 1600 Da for the lignin portion.


9

Reaction Procedure. A 1-qt emulsifying jar (Kimex) placed on a blender (Waring model 1120) with a no-load stirring rate of about 18,000 rpm was employed as the reaction system. The aqueous solution that contains the lignin and added base is placed in the reaction jar. The blender is turned on and the organic phase that contains the organostannane halide is introduced into the reaction jar. After a designated time, stirring is stopped and the blender jar contents are poured into a separatory funnel. The product is collected as a precipitate, washed repeatedly with water and the organic liquid, transferred to a preweighed glass Petri dish, and air dried. Instrumentation. Potassium bromide pellets and a Fourier transform in frared (FTIR) spectrometer (Mattson Galaxy) were used to obtain infrared spectra. Mass spectroscopy (direct insertion probe, DIP) was carried out by a mass spectrometer (Kratos MS-50) operated in the electron ionization mode, 8-kV acceleration, and a 10-s per decade scan rate with variable probe tempera ture (Midwest Center for Mass Spectrometry, Lincoln, Nebraska) and a mass spectrometer (DuPont 21-491) at 1.8 kV. Elemental analysis was carried out by Galbraith Labs (Knoxville, TN). Mossbauer spectroscopy employed a tin-119-enriched BaSn0 source at 77 °K. Solubilities were determined by placing about 3 mg of sample in approxi mately 5 mL of liquid. 3

Results and Discussion To construct the reaction conditions under which the product should contain sufficient amounts of both the flexibilizing agent and the lignin, organostan nane dichlorides were reacted with the candidate hydroxyl-capped monomers to form polymeric products: R R S n C l + H O ( C H C I I — 0 ) H -> S n — 0 ( C H C H — 0) 2

2

2

2

X

2

2

x

R R SnCl + H— 0 ( C H C H — 2

2

2

2

CHo ι

O^Si—0)(CH CH —O), -» 2

CH

2

CH,

3

I

R

(Sn—0(CH CH —O), XSi—OXCH C H —O), 2

R

2

2

CH

3


2


224

Table I. Reaction Results for Model and SIN Systems Yield

Reactants PEG(2000)-Bu SnCl PEG(2000)-La SnCl Silol(1250-Bu SnCl Silol(2000)-Bu SnCl Lignin- Bu SnCl Lignin- La SnCl 2

2

2

2

2

2

2

2


Model System 0.5937 0.4167 0.0475 0.2196 0.5311 1.8211

2

2

2

2

Silol(1250)-Bu SnCl -lignin Silol(2400)-Bu SnCl -lignin PEG(2000)-Bu SnCl -lignin PEG(2000)-La SnCl -lignin 2

2

2

2

2

2

2

2

Yield (%)

Product Number

27 17 3 10 38 100

SIN System 6.0216 7.6861 5.4155 3.0934

The results are shown in Table I. Similar reactions were carried out with lignin. Reaction was rapid, with yields of modified material produced within seconds (Table I). The yield was calculated assuming a hypothetical repeat unit that contained a single hydroxyl group. For instance, the average molecular weight for a single C unit is 178 D a . For the A T material, the hydroxyl-based repeat unit molecular weight is 302 Da. For the dihaloorganostannanes, the repeat unit is assumed to have one organostannane moiety for every two hydroxyl-based repeat units. Reactions that utilized organostannane dichlorides with a mixture of flexibilizing agent(s) and lignin were then run under the reaction conditions described in Table I. The products are believed to be intertwined with the lignin and flexibility polymers that are connected through reaction of the organostannane (Figure 1). The following connections are possible (where F is flexible moiety and L is lignin moiety). 9

LSn

L-Sn-L

L-Sn-F

F-Sn-F

The products may or may not be interpenetrating polymer networks (IPNs) because the exact nature of bonding is unknown. The products do appear to be simultaneous interpenetrating networks (SINs), where connection of the two different polymers or like polymers occurs simultaneously. Although a wide variety of organostannanes was used, emphasis will be placed on the product produced from the reaction of equal molar amounts (based on molar amounts of hydroxyl units) of hydroxyl-containing reactants and dibutyltin dichloride.



10.

CARRAHER ET AL.

225

SIN Materials

Figure 1. Simulation of the product produced from the reaction of organostannane dihalides with lignin and hydroxyl-cappedflexibilizingagents.

Reaction Conditions. The organic phase consisted of 50 m L of C H C l and the organostannane is added to rapidly (18,000 rpm, no load) stirred aqueous solutions (50 mL) of hydroxyl-containing reactants and added sodium hydroxide for 30 s stirring time at room temperature (ca 25 °C). (For the S I N reaction, 12 mequiv of each hydroxyl-containing reactant and 24 mequiv of sodium hydroxide and dibutyltin dichloride were used; half these values were used for the SIN product that contained dilauryltin dichloride). Infrared spectral results are consistent with the presence of moieties derived from each of the three reactants. For unmodified lignin, a broad intense infrared band is present from about 3400 to 2800 cm"" and is assigned to O H stretching in alcohols. The products show only a small band in this region that is consistent with the proposed substitution product. With reference to the siloxane-containing products, silicon-carbon vibrations should appear around 800 (Si—C stretch) and 1270-1250 c m ( S i — C H deforma tion) (Table II). The second band is often partially hidden by the presence of a major band at 1269 c m present in lignin (1271 c m ) . Other silicon-asso ciated bands are given in Table II. Bands associated with the formation of the S n — Ο — R moiety are given in Table III. 3

1

- 1

- 1

3

- 1


226


Table II. Infrared Band Assignments for Silicon-Containing SIN Products Band Assignment

1266

3

3


a

857, 800 700

3

7 (2400 daltons)

6(1250 daltons)

Σ

C H rock (from S i — C H ) Si—C stretch CH —Si—CH 3

Products

Frequency (cm ~ )

sh

sh

sh, + sh

+ sh

Key: sh, shoulder; +, resolved. Table III. Product S n -- O - -R Band Assignment Products

Sn—Ο—R Stretch Frequency ±5(cm~ ) v

665 598 570 a

a

Band Type

1

2

3

4

5

6

7

Model Compound

Asymmetric Symmetric Symmetric

ur ur sh

ur ur sh

ur ur ur

ur ur ur

ur ur ur

ur ur ur

ur ur ur

+ + +

Key: +, resolved; sh, shoulder; wk, weak; ur, unresolved.

Mass spectral results are also consistent with the presence of moieties from each of the three reactants. Tables I V - V I I I focus on tin-containing ion fragments found in the polyethylene glycol containing product with a probe temperature of 400 °C. In comparison to the lignin-organostannane products, new ion fragments (listed by the mass-to-charge ratio, m/e) are found at about 105 ( O C H C H O C H C H O ) , 116-119 ( H C C H O C H C H O C H C H ; C H O C H C H O C H C H 0 ) , and 73 ( H C C H O C H C H ) characteristic of polyethylene glycol (PEG). New tin-containing fragments characteristic of the presence of P E G are found at 207 ( B u S n O C H ) , 265 ( C H S n O C H C H O C H C H ) , 280 ( B u S n O O C H ) , and 295 ( B u S n O O C H C H ) . None of these ions is of sufficient intensity to perform an isotope-ion fragmentation pattern check. The chemical bonding of the P E G and lignin structures by the tin-containing moiety is also indicated by the presence of specific ion fragments. Some of these ion fragments are given in Tables V I to VIII. Again, the ion fragment intensities for these tin-containing fragments are too low to develop a tin isotope relationship as contained in Table V . 2

2

2

2

3

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

4

2

9

2

2

2

2

Mossbauer spectroscopy is especially useful to describe environments of tin-containing materials. The Mossbauer results (Table IX) are consistent with the absence of significant S n — C l bound tin. The results indicate that the tin is bound in an organic matrix that is consistent with the presence of


10.

CARRAHER ET AL.

227

SIN Materials


Table IV. Tin-Containing Ion Fragments (to m/e = 315) for the Products of Dibutyltin Dichloride, Lignin, and Hydroxyl-Capped Poly(ethylene oxide) Possible Assignment

m/e

% Relative Intensity

117 118 119 119 120 121

3.15 2.66 5.13 2.25 3.43 6.17

173 174 175 176 177 178 179

8.01 5.15 15.87 6.30 19.01 2.34 6.96

SnBu SnBu SnBu SnBu SnBu SnBu SnBu

208 210 211 212 213 214 215 217

6.30 5.32 10.71 6.82 12.86 2.46 4.57 1.68

BuSnCl, BuSnCl, BuSnCl, BuSnCl, BuSnCl, BuSnCl, BuSnCl, BuSnCl,

231 232 233 234 235

1.85 2.09 2.60 2.48 2.45

Bu Bu Bu Bu Bu

245 247

1.51 2.16

BuSnCl BuSnCl

263 266 268 271 272 273

3.41 12.12 18.56 20.59 1.72 9.98

Bu SnCl, Bu SnCl, Bu SnCl, Bu SnCl, Bu SnCl, Bu SnCl,

289 291

2.71 3.31

C H BuSnCl C H BuSnCl

311 313 315

2.10 5.00 1.96

Bu SnOOCH CH 0 Bu SnOOCH CH 0 Bu SnOOCH CH 0

SnH(116) Sn(118) SnH(118) Sn(119) Sn(120) SnH(120)

2 2 2 2 2

SnOPh SnOPh SnOPh SnOPh SnOPh SnOPh SnOPh SnOPh

Sn Sn Sn Sn Sn

2 2

2 2

2

2

2 2

BuSnOPh BuSnOPh BuSnOPh BuSnOPh BuSnOPh BuSnOPh

3

6

2

3

6

2

2

2

2

2

2

2

2

2

2



228

Table V. Relative Isotopic Ion Fragmentation for Ion Fragments Derived from BuSn for the Product of Dibutyltin Dichloride, Lignin, and PEG Sn (m/e) Sn (expected) (%) SnBu (m/e) Sn (found) (%)

116 14 173 13

117 8 174 8

118 24 175 26

119 9 176 10

120 33 177 31

122 5 178 11

124 6 181 0


Table VI. Mass Fragments Found in Indulin AT-Dibutyltin Dichloride-PEG Product X (m/e) Structure

a

—

H CH CH^CHrj CH 3CH C H 2

288 301 315 328-331

303 317 331 345

H CH CH3CH CH3CH CH

345 360 371 386

360/361

—

388 402 416

H CH CH3CHÇ2 C H 3CH C H 2

401 415 429

418

— — — —

— — —

H CH CH3CH CH3CH CH

257 271

272 288 301

288 301

301

331 345'' 360 371

345

387 401 415

401 415

R

0-OH-OH

9

OCH

9

OCH CH 9

9

R

;o

OCHo

3

ο SnOCH CH X Si Y Y = H or absent 2

2

Y = Butyl

2

3

2

2

Y = 2-Butyl

2

3

2

—

317 331 345 360

b

b

b

388 402

— — —

331 345 360

388 402 416 —

R

O SnOCH CH > Y Y = H or absent 2

Y = Butyl

2

3

—

2

2

H CH CH3CH CH3CH CH

2

—

3

2

2

Y = 2-Butyl

H CH CH CH CH3CH CH

2

—

2

2

342 356 371

3

3

298

2

399 414

— —

—

342

b

—

371 387

—

R group may be unsaturated. ' Possible background peak. 1


301 360 386 400 415

— —

10.

CARRAHER ET AL. SIN Materials

229

Table VII. Mass Fragments Found in Indulin AT-Dibutyltin Dichloride-Silol 1250 Product X (m/e) Structure

R

0-OH-OH

a

2

OCH

2

OCH CH 9

9

it

287

H

Ο SnOCH CH X 3


2

2

CH

—

3

CH CH 3

2

CH3CH CH 2

2

315 327

318

—

345

318

—

345

345 36l

b

36l

b

Y = Η or absent Y = Butyl

H

345

CH CH3CH C H 3CH 2 C H

— —

3

2

Y = 2-Butyl

H CH

2

—

3

2

H CH CH3CH CH3CH CH

2

2

416

418

— —

— —

—

—

416

— —

2

273 287 298 315

287 298 315 327

298 315 327 345

330 345 356

345 356

356

—

386

2

314 327 342 356

—

387

—

415

—

415

— —

457

2

2

—

387

387

257 271 285 298

3

2

387

2

2

CH3CH CH

—

415 429 443

3

CH CH

Ο SnOCH CH X Y

387

361

457

457 473

457 473 487

Y = H or absent Y = Butyl

H CH

3

CH CH 3

2

CH3CH CH 2

Y = 2-Butyl

H CH CH3CH2J

385

3

CH CH CH 3

a

2

2

413

—

— —

386 415

— —

— —

R group may be unsaturated. Ο group may be protonated.

the tin bound i n a S I N matrix. Currently, differentiation between Sn—Ο—alkyl and Sn—Ο—aryl groupings is not possible. Elemental analysis results help describe the complex product. The prod uct produced form the siloxane (2400 daltons) block copolymer with polyethyl ene oxide (50% by weight P E G ) , lignin, and dibutyltin dichloride had 3.55%


230


Table VIII. Mass Fragments Found in Indulin AT-Dibutyltin Dichloiide-Silol 2400 Product (400°C) X(m/e) Structure

R

—

a

0-OH-OH

2

OCH

2

OCH CH, 2

R H OCH

C 3

Ο SnOCH C H X


2

2

287

3 CH CH CH C H C H

—

H

3

315 327

2

3

2

2

— 315

315

—

—

343

—

387

343

343

—

371


H CH CH CH CH CH CH

343

—

3

2-Butyl

3

2

3

2

H CH CH CH CH CH CH

2

387

—

—

—

416

416

416

— —

457

371 387

387

—

— —

— —

— —

457

457

—

487

H CH CH CH CH CH CH

273 287 299 315

287 299 315 327

299 315 327 343

H CH CH CH H CH CH CH

415

3

3

2

3

2

2

—

R Ο SnOCH CH X 2

2

3

2

3

2

257 271 285 299

CH CH CH2

313 327 341 355

3


2-Butyl

a

3 3 3

3 3 3

2

2

CH CH CH 2

—

371

371 387

371 387

371 385

387

—

415

413

—

— —

457

—

2

2

344

—

344

—

415

415

—

— —

R group may be unsaturated.

Si and 6.49% Sn. This composition corresponds to a product that contains 18.8% block copolymer, 12.7% dibutyltin, and 68.5% lignin or for every 1 block copolymer, 7 dibutyltin moieties and 29 hydroxyl-lignin-eontaining units or 5.5 lignin molecules (assuming an average molecular weight per lignin molecule of 1600 Da). The assumption that each dibutyltin unit is doubly reacted translates to an average of two hydroxyl sites for each lignin molecule that is reacted.



10.

CARRAHER ET AL.

231

SIN Materials

In summary, spectral (Mossbauer, infrared, and mass) evidence is consis tent with a complex product with various segments as pictured in Figure 1. A thermal analysis study of the materials was accomplished. A description of selected results follows. Lignin, under a nitrogen atmosphere, shows a complex differential scanning calorimetry (DSC) thermogram from ~ 50 to 450 °C. The product of lignin and dibutyltin dichloride shows a major exotherm in the 300-400 °C range with a maximum at ~ 360-370 °C. The corresponding product (except product that also contains P E G ) shows a broad exotherm that is also in the range of 300-400 °C, but has a single maxima at about 345 °C. The corresponding products (except products that contain the ethylene oxide - dim ethylsiloxane-ethylene oxide block copolymers in place of the hydroxyl-terminated polyethylene oxide) show spectra similar to the polyethyl ene oxide-containing product with a maximum at 335 °C for the 1 2 5 0 - c m block copolymer and 340 °C for the 2400-dalton block copolymer. The dilauryltin-PEG (2000)-lignin product softens when heated to about 224 °C, but the other products derived from dibutyltin dichloride do not soften until 300 °C. Most products do compress and form semiflexible sheets when pressure (about 2000 psi) is applied at room temperature. Selected results are summarized in Table X. -1

Table IX. Mossbauer Results for the Lignin-PEG-Bu SnCl and Associated Compounds 2

^1E (mm / s) δ (mm / s) Quad. Isomer Split. Shift ΔΕ / δ

Compound Bu SnCl Lignin-PEG-Bu SnCl Lignin—Bu SnCl 2

2

2

2

2

2

2

3.42 2.97 2.97

1.61 1.23 1.23

2.46 2.46

Table X. Film-Forming Characteristics of Organostannane Products Containing Flexibilizing Agents Products AT-Dibutyltin-PEG AT-Dilauryltin-PEG AT-Dibutyltin-PEG-DMSPEG 2400

Temperature (°C) 210 180 220

Pressure (fi-lb) 20 4.5 10-15


232


Summary


The formation of simultaneous interpenetrating network (SIN) materials is indicated by F T I R and mass spectroscopy. Although non-SIN products are inflexible, the SIN products derived from coreactants that contain ethylene oxide and dimethylsilicone flexibilizing agents do offer some flexibility. Some what flexible films were formed by application of heat and pressure.

References 1. Glaser, W.; Kelley, S. Encyclopedia of Polymer Science and Engineering, 2nd ed.; Wiley: New York, 1988; Vol. 8, p 795. 2. Sperling, L.; Carraher, C. Encyclopedia of Polymer Science and Engineering, 2nd ed. Wiley: New York, 1988; Vol. 12, p 658. 3. Sperling, L.; Carraher, C. Renewable-Resource Materials; Plenum: New York, 1986. 4. Muller, P.; Glasser, W. J. Adhes. 1984, 17, 157. 5. Muller, P.; Kelley, S.; Glasser, W. J. Adhes. 1984, 17, 185. 6. Dolenko, Α.; Clarke, M . For. Prod. J. 1978, 28C8, 41. 7. Kratzl, K.; Buchtela, K.; Gratzl, J.; Zauner, J.; Ettingshausen, O. Tappi J. 1962, 45(2), 117. 8. Hsu, O.; Glasser, W. Wood Sci. 1976, 9(2), 97. 9. Glasser, W.; Hsu, O.; Reed, D.; Forte, R.; Wu, L. In Urethane Chemistry and Applications; Edwards, Kenneth N . , Ed.; ACS Symposium Series 172; American Chemical Society: Washington, DC, 1981; p 311. 10. Saraf, V.; Glasser, W. J. Appl. Polym. Sci. 1984, 29, 1831. 11. Saraf, V ; Glasser, W.; Wilkes, G.; McGrath, J. J. Appl. Polym. Sci. 1985, 30, 2207. 12. Saraf, V.; Glasser, W.; Wilkes, G. J. Appl. Polym. Sci. 1985, 30, 3809. 13. Christian, D.; Look, M.; Nobell, A. Armstrong, T. U.S. Patent 3,546,199, 1970. 14. Allan, G. U.S. Patent 3,476,795, 1969. 15. Glasser, W.; Barnett, C.; Rials, T. Saraf, V. J. Appl. Polym. Sci. 1984, 29, 1815. 16. Wu, L ; Glasser, J. J. Appl. Polym. Sci. 1984, 29, 1111. 17. Tai, S.; Nakano, J.; Migita, N . Mokuzai Gakkaishi 1967, 13, 257. 18. Tai, Α.; Nagata, M . Nakano, J.; Migita, N . Mokuzai Gakkaishi 1967, 13, 102. 19. Carraher, C.; Sterling, D. Ridgway, T.; Louda, J. W. PMSE 1991, 62, 241. 20. Seymour, R.; Carraher, C. Structure and Property Relationships in Polymers; Plenum: New York, 1984. 21. Critchfield, F. Organic Functional Group Analysis; MacMillan: New York, 1984; p 82. ;

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RECEIVED for review November 1 1 , 1 9 9 1 . ACCEPTED revised manuscript A u gust 2 6 , 1 9 9 2 .


Simultaneous Interpenetrating Network Materials Derived from

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