Synthesis, Characterization, and Properties of Poly(1-trimethylsilyl-1

Jan 20, 2012 - ... Dolzhikova , V. S. Khotimskiy. Russian Chemical Bulletin 2016 65 (4), 1067-1071 ... Maria Giovanna Buonomenna. RSC Advances 2013 3,...
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Synthesis, Characterization, and Properties of Poly(1-trimethylsilyl-1propyne)-block-poly(4-methyl-2-pentyne) Block Copolymers Eldar Yu. Sultanov,*,† Alexander A. Ezhov,†,‡ Sergey M. Shishatskiy,§ Kristian Buhr,§ and Valeriy S. Khotimskiy† †

A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky prospect, 29, 119991 Moscow, Russia M.V. Lomonosov Moscow State University, GSP-2, Leninskie Gory, 119992, Moscow, Russia § Institute of Polymer Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Str. 1, 21502 Geesthacht, Germany ‡

S Supporting Information *

ABSTRACT: Poly(1-trimethylsilyl-1-propyne)-block-poly(4-methyl-2-pentyne) (PTMSP-b-PMP) block copolymers of different composition were synthesized through sequential living polymerization by catalytic systems based on niobium pentachloride with organometallic cocatalysts in cyclohexane. Mechanical, thermal, and gas transport properties of synthesized block copolymers are investigated. The morphology of PTMSP-b-PMP can be described as a two-phase supramolecular structure which includes regions with an increased level of ordering, distributed in an amorphous phase. The observed structure of block copolymers is explained by the presence of densely packed poly(4-methyl-2-pentyne) (PMP) blocks and less ordered poly(1-trimethylsilyl-1-propyne) (PTMSP) blocks. The correlation of morphology of block copolymers with gas transport parameters as well as with resistance toward organic solvents is discussed. As result of this study, novel polymeric materials based on PTMSP and PMP combining resistance toward aromatic and aliphatic hydrocarbons with high gas transport parameters are synthesized.

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INTRODUCTION 1,2-Disubstituted polyacetylenes are nonconjugated amorphous glassy polymers with high glass transition temperatures (>200 °C) and good mechanical properties. Poly(1-trimethylsilyl-1propyne) (PTMSP) is the most studied polymer among 1,2disubstituted polyacetylenes due to its extremely high gas and vapor transport parameters.1 PTMSP also has high selectivity toward condensable hydrocarbons while separating them from mixtures with noncondensable gases. However, solubility of PTMSP in higher hydrocarbons restrains wide usage of this polymer in separation processes. Therefore, investigations are conducted to improve the properties of PTMSP, for example, by synthesizing copolymers.2−4 Another 1,2-disubstituted polyacetylenepoly(4-methyl-2-pentyne) (PMP)has high resistance toward most of organic solvents and rather high gas and vapor transport parameters, 5,6 although these parameters are lower than that of PTMSP. Several years ago random copolymers of 1-trimethylsilyl-1-propyne (TMSP) with 4-methyl-2-pentyne (MP) were synthesized,2 but they were not of high interest because of low molecular weights and poor mechanical properties. Block copolymers of TMSP with MP in contrast to random copolymers may combine properties of PTMSP and PMP. Multistage or sequential polymerization of two or more monomers is one of the main methods of block copolymer synthesis. For realization of this method a living polymerization of at least one of the monomers in chosen polymerization conditions is necessary. Effective initiation of polymerization of © 2012 American Chemical Society

second comonomer by active species of the first comonomer is also required. When these conditions are met for both monomers, it is possible to synthesize AB- and BA-type block copolymers. It is known that polymerization of substituted acetylenes by catalysts based on 5 and 6 group transition metals proceeds by the carbene mechanism.7 Since the discovery of living polymerization of substituted acetylenes8,9 many studies were carried out in this field.10,11 Living polymerization of several substituted acetylenes was used for synthesis of their block copolymers by the sequential copolymerization method.12−14 Recently, we showed15 that polymerization of TMSP and MP by the catalytic system NbCl5−Ph4Sn in cyclohexane has principal evidence of living polymerization, namely, continuation of chain propagation after addition of a new portion of the monomer, linear dependence of number-average molecular weight (Mn) on monomer conversion, and unimodal molecular weight distribution (MWD) for homopolymers obtained by sequential polymerization. It was found out16 that the continuation of chain propagation after addition of a new portion of the same monomer is observed also when the catalyst NbCl5−Ph3SiH is used during two-stage hopolymerization of TMSP or MP. Therefore, polymerization reactions of Received: September 21, 2011 Revised: December 22, 2011 Published: January 20, 2012 1222

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Scheme 1. Synthesis of AB-Type (a) and BA-Type (b) PTMSP-b-PMP Block Copolymers

The infrared (IR) spectra were measured in a range 200−4000 cm−1 on an IFS-Bruker-113-V spectrometer. A comparison of the composition of PTMSP-b-PMP estimated using IR spectra and elemental analysis data revealed their good conformity.16 Therefore, the method based on IR measurements described in ref 2 was used for calculating the composition of copolymers. Selective extraction was performed by mixing polymer product in a sample bottle with toluene for 48 h. Then the solution was filtered and the polymer fraction insoluble in toluene was dried, whereas the filtrate with soluble in toluene fraction was reprecipitated into methanol, filtrated, and dried. The weights of fractions were determined after vacuum drying. Polymer films used for X-ray diffraction analysis and measurement of mechanical properties and gas transport parameters were prepared by casting polymer solutions in cyclohexane onto cellophane. The mechanical properties of polymer films were studied at 20 °C and a constant stretching rate of 10 mm/min using an Instron-1122 instrument. The thermal properties of the polymers were investigated by differential scanning calorimetry (DSC) using a Mettler Toledo DSC823e instrument in the temperature range 20−350 °C, thermal gravimetric analysis (TGA) using a Mettler Toledo TGA/DSC-1 instrument in the temperature range 20−1000 °C, and dynamic mechanical analysis (DMA) using a Mettler Toledo DMA/SDTA861e instrument in the temperature range 20−300 °C. All measurements were performed under a nitrogen atmosphere. X-ray diffraction analysis was performed at room temperature by standard DRON-1.5 diffractometer using Cu Kα radiation (λ = 0.154 nm) under transmission and reflection modes. The samples were composed of a pile of five parallel films with a surface area of 10 × 10 mm2. The surface of polymer films was investigated by atomic force microscopy (AFM) using scanning probe microscope SOLVER PROM (NT-MDT) operated in a semicontact mode with silicon cantilevers NSG10 (NT-MDT). Films were prepared by casting polymer solutions onto silicon support at room temperature and then were annealed at 150 °C in a vacuum oven. Single gas transport properties of H2, He, N2, O2, CH4, CO2, and nC4H10 gases for polymer films were determined with a constantvolume/variable-pressure (time-lag) method at 30 °C. CH4 and n-C4H10 mixed gas permeation experiments were carried out with the experimental setup described by Yave et al.19 The gas mixture was prepared directly before measurement by mixing individual gases CH4 (purity 99.999%) and n-C4H10 (purity 99.5%). The gas flow and pressure of feed and sweep (N2) were measured on entrance to the measurement cell. The compositions were analyzed by an Agilent 9890N gas chromatograph.

TMSP and MP by NbCl5−Ph4Sn and NbCl5−Ph3SiH have living nature under the same conditions. This paper reports on the synthesis of AB- and BA-type PTMSP-b-PMP block copolymers through sequential living polymerization of TMSP and MP by NbCl5-based catalyst and the investigation of properties of these block copolymers.

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EXPERIMENTAL PART

Materials. Monomers TMSP (99.9%) and MP (99.9%) were synthesized by techniques developed in cooperation with NPO OAO Yarsintez.17,18 Monomers and cyclohexane (99%, Fluka) were distilled three times over calcium hydride under high-purity argon before polymerization experiments. Catalyst niobium pentachloride, NbCl5 (99.5%, Fluka), and cocatalysts tetraphenyltin, Ph4Sn (97%, Fluka), triphenylsilane, Ph3SiH (97%, Fluka), triethylsilane, Et3SiH (97%, Fluka), and tetrabutyltin, Bu4Sn (98%, Fluka), were used as received. Block Copolymer Synthesis. The synthesis of PTMSP-b-PMP was carried out by sequential polymerization according to one of the reactions in Scheme 1. The second monomer was added to the reaction mixture with living active species of the polymer being formed at the first stage of polymerization. (Here and everywhere conversion at the first stage of sequential polymerization is accepted as 100% because polymerization was carried out in conditions in which 100% yield of polymer is observed16.) The synthesis of AB-type PTMSP-b-PMP (Scheme 1a) was performed according to the following technique. A glass reactor was loaded with a solution of NbCl5 (0.15 g, 0.55 mmol) and Ph4Sn (0.24 g, 0.55 mmol) in cyclohexane (28 mL). The resulting mixture was vigorously stirred at 25 °C for 30 min in a flow of high-purity argon. Then, TMSP (3.08 g, 27.5 mmol) was added to the catalytic solution. After 24 h (during this time, 100% conversion of added TMSP was achieved) the second monomer, MP (2.26 g, 27.5 mmol), in 28 mL of cyclohexane was added to the reaction mixture. After 72 h the reaction mixture was treated with methanol (50 mL) to deactivate the catalyst. The polymer was dissolved in CCl4 (300 mL), precipitated into methanol (1.5 L), filtered out, and dried in the air for 24 h. The resulting polymer was redissolved in CCl4 and reprecipitated into methanol. After vacuum drying, the yield of the product was determined. The synthesis of BA-type PTMSP-b-PMP was performed in a similar manner, but monomers (TMSP and MP) were added to the reactor in reversed order (Scheme 1b). Measurements. Molecular weight characteristics were determined by gel-permeation chromatography (GPC). Measurements were performed in cyclohexane at 20 °C using a Waters chromatograph equipped with a Waters R401 refractometric detector and a system of 2 × PLgel 5 μ MiniMix-C columns. The molecular weight parameters were estimated from the calibration plot constructed on the basis of samples of PTMSP and PMP with determined molecular weights (these samples were characterized by GPC using a chromatograph equipped with light scattering and refractometric detectors). The intrinsic viscosity of polymer solutions in CCl4 was measured at 25 °C using an Ostwald−Ubbelohde viscometer. The 1H nuclear magnetic resonance (NMR) spectra of polymer solutions in CDCl3 or C6D12 were recorded on Bruker MSh-300 instrument operating at 300 MHz.

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RESULTS AND DISCUSSION Selection of Conditions for Synthesis of PTMSP-bPMP. The study of polymerization reactions of TMSP and MP in cyclohexane by common effective NbCl5-based catalysts with organometallic cocatalysts showed that 100% yield of both PTMSP and PMP is observed on two catalytic systems: NbCl5−Ph4Sn and NbCl5−Ph3SiH (Table 1). Samples of 1223

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steric accessibility of the CC bond. It is worth noting that the initiation efficiency of polymerization for both TMSP and MP by NbCl5-based catalysts is rather low ( 2 × 105) and high intrinsic viscosities ([η] > 0.5 dL/g) of obtained polymers. Stirring and heat exchange decrease as viscosity of polymerization mixture increases, and as a result synthesis of polymer with high molecular weight and narrow MWD is complicated.20 One more factor that influences the polydispersity is a difference in propagation and initiation rates of polymerization. Widening of MWD is observed when propagation rate is higher than initiation rate, and this effect also may take place during polymerization of TMSP and MP monomers.8 As shown in Table 1 at the same conditions during PMP synthesis, polymers with higher molecular weights are formed than in case of PTMSP synthesis. This is evidently related to the fact that in case of polymerization of TMSP more active species are formed. Initiation efficiency of polymerization for monomers TMSP and MP can be calculated from [P*]/[Cat.] = [M]consumed/(DP × [Cat.]), where [M] is the monomer concentration, DP the degree of polymerization, and [Cat.] the catalyst concentration. Polymerization initiation efficiency for TMSP is equal to 2.2% and 2.3%, while for MP is equal to 0.8% and 1.2% by catalysts NbCl5−Ph4Sn and NbCl5−Ph3SiH, respectively. So it can be concluded that efficiency of polymerization by aforementioned catalytic systems for TMSP is higher than for MP. Matson et al.2 have also mentioned that TMSP is more active than MP due to better

Table 2. Results of Synthesis of PTMSP-b-PMP and Their Extraction in Toluenea soluble in toluene run

catalyst

M1

M1/M2 in feedb

M1/M2 in productc

yield (%)

Mn × 10−5

Mw/Mn

amount (%)

TMSP/MPd

1 2 3 4 5e 6e 7e 8e

NbCl5−Ph4Sn NbCl5−Ph3SiH NbCl5−Ph4Sn NbCl5−Ph3SiH NbCl5−Ph4Sn NbCl5−Ph3SiH NbCl5−Ph4Sn NbCl5−Ph3SiH

TMSP TMSP MP MP TMSP TMSP MP MP

50:50 50:50 50:50 50:50 33:67 33:67 33:67 33:67

60:40 60:40 90:10 75:25 40:60 35:65 65:35 40:60

79 80 21 58 78 85 54 83

3.1 3.5 5.8 5.1 3.7 4.0 6.7 6.3

2.1 2.2 2.2 2.4 2.7 2.5 2.9 2.7

100 100 0 0 64 55 43 58

60:40 60:40

70:30 50:50 80:20 75:25

insoluble in toluene amount (%)

TMSP/MPd

0 0 100 100 36 45 57 42

10:90 25:75 15:85 15:85 25:75 35:65

Polymerization was carried out in [M1]0 = 1 mmol/L; [Cat.] = [Cocat.] = 20 mmol/L; solvent: cyclohexane; T = 25 °C; M1 = the first monomer to the solution of which after 24 h the second monomer (M2) was added; yield = yield of the second stage of sequential copolymerization after 72 h. b Molar ratio M1:M2 added to the reactor. cMolar ratio M1:M2 in the products of copolymerization. dMolar ratio TMSP:MP in the copolymer. e Temperature of the second stage of the sequential copolymerization equals 75 °C. a

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Figure 1. Typical IR spectra of (a) PTMSP (dashed line) and PMP (solid line) and (b) PTMSP-b-PMP.

Figure 2. Typical 1H NMR spectrum of PTMSP-b-PMP.

2, runs 1 and 2). As a result, completely soluble in toluene block copolymers containing up to 40% second block (PMP) were obtained. As seen in Figure 3a, synthesized block copolymers have higher molecular weights than PTMSP sample obtained at similar conditions. The synthesis of BA-type PTMSP-b-PMP, i.e., sequential copolymerization by addition of TMSP monomer to the living PMP, proceeds with rather low yield (≤60%) at the second stage (Table 2, runs 3 and 4). Obtained block copolymers contain up to 25% second block (PTMSP), are completely insoluble in toluene, and have higher molecular weights than PMP homopolymer synthesized at similar conditions (Figure 3b). In the case of sequential polymerization performed with double excess of second monomer and at higher temperature of second stage equal to 75 °C, it is possible to increase the yield during synthesis of both AB- and BA-type block copolymers. As a result, a mixture of copolymers with different block ratios is formed (Table 2, runs 5−8) which by extraction in toluene can be divided into two fractions: soluble fraction enriched with TMSP units and insoluble fraction enriched with MP units.

Figure 3. GPC traces of samples: (a) PTMSP (dashed line) and ABtype PTMSP-b-PMP (solid line); (b) PMP (dashed line) and BA-type PTMSP-b-PMP (solid line).

It is significant that a diffusion factor also plays a big role when polymerization proceeds in highly viscous and heterogeneous conditions as in the case of the second stage of sequential polymerization of TMSP and MP monomers. That is why we 1225

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Figure 4. Behavior of storage modulus E′ (dashed line), loss modulus E″ (solid line), and tan(δ) (dash-dotted line) as a function of temperature for PMP (a), PTMSP (b), and PTMSP-b-PMP block copolymers with the block ratio of 35:65 (c) and 60:40 (d).

of obtained block copolymers which is also typical for PTMSP and PMP homopolymers. DMA data indicate that storage modulus (E′) of PTMSP-bPMP block copolymers falls at temperatures which are lower than decomposition temperatures of these samples. Therefore, DMA was used to determine glass transition temperatures of PTMSP-b-PMP, PTMSP, and PMP (Figure 4). DMA data indicate that the glass transition temperature for PTMSP-bPMP with block ratios of 35:65 and 60:40 equals 245 and 265 °C, respectively, and for PMP equals 240 °C. The storage modulus of PTMSP almost does not change until its decomposition temperature equals 280 °C. So the glass transition temperature of PTMSP is higher than its decomposition temperature, and owing to this, it is not possible to determine the glass transition temperature of PTMSP and consequently the second glass transition temperature of PTMSP-b-PMP. It was found out glass transition temperatures of block copolymer samples are close to glass transition temperature of PMP homopolymer, which indicates the presence of PMP phase in these block copolymers. Dependence of glass transition temperature on composition of PTMSP-b-PMP can be related to existence of diffuse interface between PTMSP and PMP phases, which is a result of their chemical affinity. The supramolecular structure of block copolymers was studied by X-ray diffraction analysis (Table 3). The scattering

suppose that the reason for broad MWD of copolymerization products as well as the cause for formation of a mixture of block copolymers with different composition is related to the high viscosity of the polymerization solutions. Low yields of BA-type PTMSP-b-PMP can be also explained by high viscosity of PMP solution formed at the first stage of sequential copolymerization (intrinsic viscosity of PMP [η] > 2 dL/g). Uniform stirring and monomer diffusion are considerably hindered when TMSP is added to such viscous PMP solution at the second stage of copolymerization, and this may slow down the polymerization. As a result of sequential copolymerization reactions, PTMSPb-PMP block copolymers with different block ratios were obtained. Since the type (AB or BA) of PTMSP-b-PMP used for further investigations does not play a big role, only block ratios of block copolymers are undermentioned. Properties and Morphology of PTMSP-b-PMP. Obtained block copolymers are colorless amorphous polymers with good film-forming and mechanical properties. Block copolymers have strength, σ = 33−42 MPa; strain break, ε = 25−60%; and Young’s modulus, E = 1000−1300 MPa, depending on their composition, and these properties increase with MP content. TGA experiments showed that decomposition of PTMSP-bPMP starts at 260−280 °C and meaning high thermal stability 1226

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the lateral size (10−100 nm), and perhaps this is due to high heterogeneity in macrochain packing. The lateral size of clusters in films from PTMSP-b-PMP block copolymers increases with the content of TMSP units (Figure 5c,d). It should be noted that these changes does not correlate with changes in average molecular weight. The most probable reason for increase in lateral size of clusters is decrease of average packing density with increase of TMSP content in PTMSP-b-PMP, and this corresponds to X-ray data. On scales of hundreds of nanometers can be seen that the inhomogeneity of the film surface increases with the content of TMSP units. At the same time the mean force of probe interaction with surface which leads to modification of the surface during AFM measurements decreases with increase of TMSP content. This fact can be interpreted as decrease of surface strength of polymer film. As a rule, the decrease of strength correlates with the decrease of the chain packing density. Resistance of block copolymers toward organic solvents depends on composition of block copolymers (Table 4). All obtained samples can be divided into two groups: block copolymers enriched with MP units which are resistant toward aromatic and aliphatic hydrocarbons and block copolymers enriched with TMSP units which are soluble in a wide range of nonpolar and weak-polar organic solvents (for example, THF, octane, toluene, benzene, etc.). Block copolymers enriched with MP units have more ordered regions with high density of macrochain packing and as a result have high resistance toward organic solvents which is similar to PMP homopolymer. Probably, densely packed PMP blocks in PTMSP-b-PMP block copolymers act as physical cross-links responsible for resistance of polymer toward organic solvents. The presence of PMP phase in block copolymers enriched with MP units is confirmed

Table 3. X-ray Data for PTMSP-b-PMP, PTMSP, and PMP Samples

a

sample

2θ, deg

Δ1/2, deg

d,b nm

PMP 35:65a 60:40a PTMSP

11.4 10.2 9.7 9.2

1.9 2.9 3.2 2.4

0.776 0.838 0.941 0.955

PTMSP/PMP block ratio in PTMSP-b-PMP. bInterplanar spacing.

profile shows an amorphous-like pattern and displays diffuse maximum with angular position of 2Θ equal to ∼10° and with half-width ∼3°. This indicates that, although the coherent scattering region is small, it is larger than in the case of truly amorphous polymers, for which the reflection half-width is usually 5°−8°.22 In terms of supramolecular ordering the structure of block copolymers can be defined as a certain state intermediate between liquidlike truly amorphous and ordered states (crystalline or semicrystalline). The X-ray data indicate that block copolymers possess a two-phase structure characterized by presence of less ordered regions and regions with an increased level of ordering. On the basis of the value of interplanar spacing, it can be concluded about macrochain packing. Increase of interplanar spacing with enhance of TMSP content in block copolymers indicates that packing density decreases. The surface of PTMSP-b-PMP films as well as PMP and PTMSP films was studied by AFM (Figure 5). The surface of PMP and PTMSP-b-PMP films can be described as consisting of clusters of similar size (10−40 nm), typical for each sample (Figure 5a,c,d). The surface of PTMSP film consists of formations (Figure 5b), which have a widespread of values of

Figure 5. AFM images (topography, 400 × 400 nm) of the films from PMP (a), PTMSP (b), and PTMSP-b-PMP block copolymers with the block ratio of 35:65 (c) and 60:40 (d). 1227

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content in block copolymers increase of permeability coefficients is observed. Results of separation of n-butane/methane mixture by films from PTMSP-b-PMP are presented in Table 6. Selectivity of

Table 4. Resistance of PTMSP-b-PMP Block Copolymers toward Organic Solventsa solvent sample

heptane, octane

toluene, benzene

THF

cyclohexane

CCl4

PMP 10:90b 25:75b 35:65b 50:50b 60:40b 75:25b PTMSP

− − − − + + + +

− − − − + + + +

− − − − + + + +

+ + + + + + + +

+ + + + + + + +

Table 6. n-Butane/Methane (2 mol %/98 mol %) Gas Mixture Permeability (P) and Selectivity for PTMSP-b-PMP, PMP, and PTMSP Samples P, barrer

“+”, polymer is soluble at room temperature; “−”, polymer is insoluble at room temperature. bPTMSP/PMP block ratio in PTMSPb-PMP. a

a

by DMA data since glass transition temperatures for PTMSP-bPMP with block ratio of 35:65 and PMP homopolymer are almost equal (245 and 240 °C, respectively). With a rise of TMSP content the packing of block copolymers become less ordered, and it is most likely that PMP blocks are gradually transforming to an intermediate phase or a diffuse interface, i.e., a phase where both PMP and PTMSP blocks are randomly mixed. Densely packed ordered regions change into less ordered or disordered regions, and PMP blocks no longer perform the role of physical cross-links. As a result, resistance of block copolymers toward hydrocarbons is decreased, and they have solubility similar to PTMSP, despite the presence of PMP blocks. It is well-known that resistance of disubstituted polyacetylenes toward organic solvents strongly depends on the supramolecular packing.23 In turn, supramolecular packing of PTMSP and PMP depends on their geometry, i.e., cis/trans ratios.6,23 Therefore, cis/trans content of PTMSP, PMP, and PTMSP-b-PMP block copolymers was calculated using their 13 C NMR spectra (see Supporting Information Figures S1 and S2). Blocks of PTMSP and PMP in PTMSP-b-PMP block copolymers have the same cis/trans ratios as PTMSP and PMP homopolymers, which are equal to 65:35 and 50:50, respectively. Single gas permeability through PTMSP-b-PMP films is presented in Table 5. (Several films were retested after 30 days, and results showed that decrease of permeabilities does not exceed 10%.) As expected, it is possible to regulate gas permeability by varying the composition of PTMSP-b-PMP. The presence of PTMSP blocks with high free volume provides a high level of gas permeability, and by enhancing the TMSP

sample

CH4

C4H10

mixed gas selectivity α(C4H10/CH4)

PMP 35:65a 60:40a PTMSP

770 990 1100 2200

7200 14000 20000 68000

9 14 18 31

selectivity calcd from single gas permeability α(C4H10/CH4) 2.5 2.4 2.8 3.5

PTMSP/PMP block ratio in PTMSP-b-PMP.

mixture separation is much higher than ideal selectivity calculated from permeability coefficients of pure gases. This is also characteristic for polymers PTMSP and PMP and can be explained as that during separation of mixture of condensable and noncondensable gases by dense polymer films the condensable vapor sorbs onto free volume elements or small “pores”, eventually producing multilayer adsorption or even capillary condensation.24 In this case the pores are partially or completely filled by adsorbed vapor and such a blockage reduces the flow of the noncondensable gases. As a result, the membrane is highly permeable to the condensable gas but significantly less permeable to noncondensable gas. Thus, during separation of n-butane/methane mixture transport of methane is blocked by n-butane condensed at the free volume elements. The dependence of n-butane/methane selectivity on block ratio of the block copolymers may be due to changes in the level of free volume of PTMSP-b-PMP. Thus, increase in free volume contributes to the sorption of condensable molecules of n-butane, which leads to an increase in n-butane permeability.

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CONCLUSION Novel block copolymers were synthesized through sequential living polymerization of TMSP and MP by NbCl5-based catalytic systems. It is possible to influence composition and properties of block copolymers by variation of monomer addition sequence and initial ratio of monomers. Furthermore, selective extraction of copolymerization products allows obtaining PTMSP-b-PMP in a wide range of TMSP/MP

Table 5. Pure Gas Permeability Coefficients (P) for PTMSP-b-PMP, PMP, and PTMSP Samples P, barrera

a

sample

H2

He

N2

O2

CO2

CH4

C4H10

PMP 10:90b 25:75b 35:65b 50:50b 60:40b 75:25b PTMSP

3500 4700 5750 6800 7600 8200 10000 13000

1600 2200 2600 3000 3250 3400 4000 5300

800 1000 1450 1700 2150 2400 3100 5200

1700 2300 2750 3300 3800 4100 5100 7500

7500 11000 13500 15000 17000 18000 22000 28000

2000 2800 3500 4100 5200 5900 8200 14000

5000 6800 8900 10000 14000 17000 26000 49000

1 barrer = 1 × 10−10 cm3 (STP) × cm × cm−2 × s−1 × (cmHg)−1. bPTMSP/PMP block ratio in PTMSP-b-PMP. 1228

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(17) Surovtsev, A. A.; Petrushanskaya, N. V.; Karpov, O. P.; Khotimskiy, V. S.; Litvinova, E. G. RF Patent 2228323, 2004. (18) Litvinova, E. G.; Melekhov, V. M.; Petrushanskaya, N. V.; Roscheva, G. V.; Fedotov, V. B.; Feldblyum, V. Sh.; Khotimskiy, V. S. RF Patent 1823457, 1993. (19) Yave, W.; Peinemannn, K.-V.; Shishatskiy, S.; Khotimskiy, V.; Chirkova, M.; Matson, S.; Litvinova, E.; Lecerf, N. Macromolecules 2007, 40, 8991−8998. (20) Johnson, A. F.; Mohsin, M. A.; Meszena, Z. G.; Graves-Morris, P. Polym. Rev. 1999, 39, 527−560. (21) Ivin, K. J.; Milligan, B. D. Makromol. Chem., Rapid Commun. 1987, 8, 269−271. (22) Ovchinnikov, Yu. K.; Antipov, E. M.; Markova, G. S.; Bakeev, N. F. Makromol. Chem. 1976, 177, 1567. (23) Khotimsky, V. S.; Tchirkova, M. V.; Litvinova, E. G.; Rebrov, A. I.; Bondarenko, G. N. J. Polym. Sci., Part A: Polym. Chem. 2003, 41, 2133−2155. (24) Pinnau, I.; Toy, L. G. J. Membr. Sci. 1996, 116, 199−209.

content ratio (from 15:85 to 80:20). Results of selective extraction, GPC, and IR and NMR spectroscopy testify formation of block copolymers of TMSP with MP. PTMSP-b-PMP block copolymers have high thermal stability and good mechanical properties. The studies of supramolecular structure indicate that PTMSP-b-PMP possess a two-phase structure characterized by presence of regions with an increased level of ordering dispersed in amorphous polymer matrix. The macrochain packing of block copolymers enriched with TMSP units becomes less dense and less ordered. Thus, in PTMSP-bPMP block copolymers gas transport parameters increase with TMSP units content, whereas resistance toward organic solvents increases with MP units content.

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ASSOCIATED CONTENT

S Supporting Information *

13

C NMR spectra of PTMSP, PMP, and PTMSP-b-PMP block copolymers and calculation of their cis/trans content. This material is available free of charge via the Internet at http:// pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*Tel +7 495 9554205; Fax +7 495 6338520; e-mail sultanov@ ips.ac.ru.

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ACKNOWLEDGMENTS This work was supported by the Russian Foundation of Basic Research, project 07-03-00553, and the Ministry of Education and Science of the Russian Federation (GK No. 16.516.11.6140). The authors thank G. N. Bondarenko, M. Yu. Gorshkova, and G. A. Shandryuk for their experimental help.

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dx.doi.org/10.1021/ma202140c | Macromolecules 2012, 45, 1222−1229