Synthesis and characterization of copolymers based on poly(butylene terephthalate) and ethylene oxide‐poly(dimethylsiloxane)‐ethylene oxide

A series of thermoplastic elastomers based on ethylene oxide‐poly(dimethylsiloxane)‐ethylene oxide (EO‐PDMS‐EO), as the soft segment, and poly(butylene terephthalate) (PBT), as the hard segment, were synthesized by catalyzed two‐step, melt transesterification reaction of dimethyl terephthalate (DMT) with 1,4‐butanediol (BD) and α,ω‐dihydroxy‐(EO‐PDMS‐EO). Copolymers with a content of hard PBT segments between 40 and 90 mass % and a constant length of the soft EO‐PDMS‐EO segments were prepared. The siloxane prepolymer with hydrophilic terminal EO units was used to improve the miscibility between the polar comonomers, DMT and BD, and the nonpolar PDMS. The molecular structure and composition of the copolymers were determined by ¹H‐NMR spectroscopy, whereas the effectiveness of the incorporation of α,ω‐dihydroxy‐(EO‐PDMS‐EO) into the copolymer chains was verified by chloroform extraction. The effects of the structure and composition of the copolymers on the melting temperatures and the degree of crystallinity, as well as on the thermal degradation stability and some rheological properties, were studied. It was demonstrated that the degree of crystallinity, the melting and crystallization temperatures of the copolymers increased with increasing mass fraction of the PBT segments. The thermal stability of the copolymers was lower than that of PBT homopolymer, because of the presence of thermoliable ether bonds in the soft segments. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A new macroinitiator for the synthesis of triblock copolymers PA12‐b‐PDMS‐b‐PA12

A new PDMS macroinitiator is proposed for the anionic ring‐opening polymerization of lactams. This α,ω‐dicarbamoyloxy caprolactam PDMS macroinitiator was readily obtained in quantitative yield, by an original synthesis scheme in two steps, which involved the scarcely reported reaction of isocyanates with silanol groups. It was then shown that this bifunctional macroinitiator enabled to synthesize triblock copolymers PA12‐b‐PDMS‐b‐PA12 by polymerization of lauryl lactam (LL) at high temperature (200°C) in inert atmosphere under conditions compatible with reactive extrusion processes. Another related high molar weight α,ω‐diacyllactam PDMS macroinitiator was also successfully used in the polymerization of LL under the same conditions, therefore overcoming the limitations formerly reported for this type of macroinitiators during the polymerization ε‐caprolactam (ε‐CL) at a much lower temperature (80°C). Triblock copolymers with a wide range of PA12 /molar weights (M_n: ～ 10,800–250,000 Da) were eventually obtained by using both types of macroinitiators. DMTA and DSC analyses showed that their thermal properties were strongly dependent upon their respective contents in soft and hard blocks. Such triblock copolymers already appear very promising for the highly effective in situ compatibilization of PA12/PDMS blends as shown by recent complementary results obtained in our laboratory. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 102: 2818–2831, 2006     

Surface microphase separation in PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films

Well‐defined poly(dimethylsiloxane)‐block‐poly(methyl methacrylate)‐block‐poly(2,2,3,3,4,4,4‐heptafluorobutyl methacrylate) (PDMS‐b‐PMMA‐b‐PHFBMA) triblock copolymers were synthesized via atom transfer radical polymerization (ATRP). Surface microphase separation in the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films was investigated. The microstructure of the block copolymers was investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Surface composition was studied by X‐ray photoelectron spectroscopy (XPS). The chemical composition at the surface was determined by the surface microphase separation in the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films. The increase of the PHFBMA content could strengthen the microphase separation behavior in the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films and reduce their surface tension. Comparison between the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymers and the PDMS‐b‐PHFBMA diblock copolymers showed that the introduction of the PMMA segments promote the fluorine segregation onto the surface and decrease the fluorine content in the copolymers with low surface energy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Investigation on isothermal crystallization,melting behaviors,and spherulitic morphologies of multiblock copolymers containing poly(butylene succinate) and poly(1,2‐propylene succinate)

In this article, isothermal crystallization, melting behaviors, and spherulitic morphologies of high‐impact multiblock copolymers, comprising of PBS as hard segment and poly(1,2‐propylene succinate) (PPSu) as soft segment with hexamethylene diisocyanate as a chain extender, were investigated. The results from differential scanning calorimetry (DSC) suggest that the two segments of multiblock copolymers are miscible in amorphous region. The crystallization kinetics were analyzed by the Avrami equation. The effect of PBS segment length as well as the introduction of PPSu segment on the crystallization kinetics and melting bebaviors of block copolymers was studied. Both crystallization rate (G) and spherulitic growth rate (g) are markedly increased with the increase of PBS segment length or decreased with the incorporation of PPSu segment. All the multiblock copolymers show the multiple melting behaviors, whose position and area depend on PBS segment length and the presence of PPSu segment. The melting peaks shift to higher temperature region with increasing PBS segment length. Spherulitic morphologies of the multiblock copolymers after being isothermally crystallized were examined by polarized optical microscopy. It is the first time to investigate the effect of one segment length on crystallization bebavior of block copolymers based on a fixed weight ratio systematically. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Microphase separation behavior on the surfaces of poly(dimethylsiloxane)‐block‐poly(2,2,3,3,4,4,4‐heptafluorobutyl methacrylate) diblock copolymer coatings

Microphase separation behavior on the surfaces of poly(dimethylsiloxane)‐block‐poly(2,2,3,3,4,4,4‐heptafluorobutyl methacrylate) (PDMS‐b‐PHFBMA) diblock copolymer coatings was investigated. The PDMS‐b‐PHFBMA diblock copolymers were successfully synthesized via atom transfer radical polymerization (ATRP). The chemical structure of the copolymers was characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy. Surface composition was studied by X‐ray photoelectron spectroscopy. Copolymer microstructure was investigated by atomic force microscopy. The microstructure observations show that well‐organized phase‐separated surfaces consist of hydrophobic domain from PDMS segments and more hydrophobic domain from PHFBMA segments in the copolymers. The increase in the PHFBMA content can strengthen the microphase separation behavior in the PDMS‐b‐PHFBMA diblock copolymers. And the increase in the annealing temperature can also strengthen the microphase separation behavior in the PDMS‐b‐PHFBMA diblock copolymers. Moreover, Flory‐Huggins thermodynamic theory was preliminarily used to explain the microphase separation behavior in the PDMS‐b‐PHFBMA diblock copolymers.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Structure and thermal behavior of nylon‐6/polytetrahydrofuran triblock copolymers obtained via anionic polymerization

The structure, crystallization, and phase behavior of nylon6‐b‐polytetrahydrofuran‐b‐nylon6 triblock copolymers synthesized via activated anionic polymerization have been studied. The composition, molecular weight of polytetrahydrofuran (PTHF) soft block, and type of polymeric activators (PACs) have been varied. Differential Scanning Calorimetry (DSC), Wide‐Angle X‐ray Diffraction (WAXD), Transmission Electron Microscopy (TEM), and Polarized Light Microscopy (PLM) experiments have revealed that in triblock copolymers only the nylon‐6 component crystallizes while PTHF segments are amorphous. The soft blocks do not alter the spherulitic crystalline structure of nylon‐6 and hard blocks crystallize in the α‐modification. The degree of crystallinity decreases with increasing PTHF concentration. The phase behavior has been investigated by Dynamic Mechanical Thermal Analysis (DMTA). Two different glass transition temperatures (T_g) for all samples have been observed. This indicates that nylon‐6 and PTHF segments are not molecularly miscible and the copolymers are microphase separated. The mechanical properties of the copolymers synthesized have been evaluated. Nylon‐6 copolymers with soft block concentrations up to 10 w/w %, exhibit improved notched impact strength in comparison to the nylon‐6 homopolymer, retaining relatively high hardness and tensile strength. All copolymers possess low water absorption and good thermal stability. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1448–1456, 2002; DOI 10.1002/app.10448     

Surface properties of block and graft polystyrene–polydimethylsiloxane copolymers

The surface compositions of a series of polystyrene‐b‐polydimethylsiloxane (PS‐b‐PDMS) and polystyrene‐g‐polydimethylsiloxane (PS‐g‐PDMS) copolymers were investigated using ATR‐FTIR and XPS technique. The results showed that enrichment of PDMS soft segments occurred on the surface of the block copolymers as well as on that of graft copolymers. And the magnitude order of the enrichment was as follows: PS‐b‐PDMS > PS‐g‐PDMS, which was attributed to the facilitating of the movement of the PDMS segments in PS‐b‐PDMS copolymer. Meanwhile, the solvent type and the contact medium had influence on the accumulation of PDMS on the surfaces. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Crystallization and thermal properties of biodegradable polyurethanes based on poly[(R)‐3‐hydroxybutyrate] and their composites with chitin whiskers

A series of biodegradable polyurethanes (PUs) were synthesized from hydroxylated bacterial poly[(R)‐3‐hydroxybutyrate], P[(R)‐HB]‐diol, as crystallizable hard segment and hydroxyl‐terminated synthetic poly[(R,S)‐3‐hydroxybutyrate), P[(R,S)‐HB]‐diol, as an amorphous soft segment, using 1,6‐hexamethylene diisocyanate, as non‐toxic connecting agent. The P[(R)‐HB] content was varied from 30 to 70 wt %. The resulting copolymers were characterized by FT‐IR, ¹H‐NMR, DSC, and TGA. The DSC data revealed that the melting of P[(R)‐HB] segment increases with increasing its own content in the PUs. The cold and melt crystallization are enhanced with increasing P[(R)‐HB] content. The TGA data revealed that the thermal decomposition mainly occurred via a single degradation step and the thermal stability slightly increased with increasing P[(R)‐HB] content. The non‐isothermal crystallization behavior of PU sample containing 40 wt % PHB with and without α‐Chitin whiskers was studied using DSC, and their kinetics data were investigated via the Avrami, Ozawa, and Z.S. Mo methods, respectively. Crystallization activation energy was estimated using Kissinger's method. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40784.     

Synthesis and characterization of poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) triblock copolymers with dibutylmagnesium as catalyst

Two series of poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) triblock copolymers were prepared by the ring opening polymerization of ε‐caprolactone in the presence of poly(ethylene glycol) and dibutylmagnesium in 1,4‐dioxane solution at 70°C. The triblock structure and molecular weight of the copolymers were analyzed and confirmed by ¹H NMR, ¹³C NMR, FTIR, and gel permeation chromatography. The crystallization and thermal properties of the copolymers were investigated by wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). The results illustrated that the crystallization and melting behaviors of the copolymers were depended on the copolymer composition and the relative length of each block in copolymers. Crystallization exothermal peaks (T_c) and melting endothermic peaks (T_m) of PEG block were significantly influenced by the relative length of PCL blocks, due to the hindrance of the lateral PCL blocks. With increasing of the length of PCL blocks, the diffraction and the melting peak of PEG block disappeared gradually in the WAXD patterns and DSC curves, respectively. In contrast, the crystallization of PCL blocks was not suppressed by the middle PEG block. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polyether‐amide segmented copolymers based on ethylene terephthalamide units of uniform length

Segmented copolymers were synthesized using the crystallizable bisesterdiamide segment (N,N′‐bis(p‐carbomethoxybenzoyl)ethanediamine) T2T‐dimethyl (a one‐and‐a‐half repeating unit of nylon 2,T) and poly(tetramethyleneoxide) segments. Poly(tetramethyleneoxide) (PTMO) is amorphous and has a low T_g. The segment length was varied from 650 to 2800 g/mol by extending PTMO₆₅₀ using dimethyl isophthalate. The polymers were synthesized in the melt, and test samples were prepared by injection molding. The melting behavior, as well as the torsion modulus spectrum as a function of temperature, were studied using DSC and DMA, respectively. The T2T‐PTMO polymers were found to have sharp glass (T_g) and flow transitions (T_fl), and the modulus at the rubbery plateau appeared to be virtually temperature independent. The T_g value was found to be independent of the diamide concentration, thus indicating that the T2T segments were fully crystallized. The T_fl was found to decrease with increasing soft segment length; this was ascribed to a “solvent” effect of the amorphous phase of the crystalline T2T units. The difference between the melting and crystallization temperatures was found to be low, thus suggesting that on cooling, there is a high rate of crystallization. When ethanediol was added as a T2T segment extender, amide‐ester‐amide segments were introduced. These amide‐ester‐amide segments form a separate lamellar phase with a much higher melting temperature (>300°C). It was found that the crystallization rate of the T2T units was enhanced by the presence of the amide‐ester‐amide segments, indicating that upon cooling, the crystallized amide‐ester‐amide segments form the nucleation sites for the nonextended T2T segments. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1173–1180, 2001     

The effect of the mass ratio of hard and soft segments on some properties of thermoplastic poly(ester‐siloxane)s

A series of thermoplastic elastomers based on soft polydimethylsiloxane (PDMS) and hard poly(butylene terephthalate) (PBT) segments was synthesized using a two‐step transesterification reaction in the melt. The molar mass of the soft PDMS component was constant (M?_nPDMS = 1056 g mol^?1) while the starting reaction mixture compositions were varied to obtained copolymers with a mass ratio of hard to soft segments in the range from 70/30 to 40/60. The structure and composition of the copolymers was verified by ¹H NMR spectroscopy. It appeared that there was a pronounced molar mass maximum when the PBT content of the copolymers was approximately 60 mass%, whereas all samples were considerably inhomogeneous with respect to the distribution of the lengths of the hard segments. Differential scanning calorimetry (DSC) thermograms showed that the melting and crystallization temperature increased with increasing PBT content, as did the total degree of crystallinity, which was confirmed by wide‐angle X‐ray scattering (WAXS) analysis. Thermogravimetric analysis (TGA) performed in nitrogen gave subtle differences for samples of different composition, including that of the PBT homopolymer, whereas in oxygen these differences were more pronounced in the way the thermo‐oxidative stability of the obtained copolymers decreased with decreasing PBT content. Finally, it was shown that the hardness depended directly on the PBT content, ie the higher the PBT content, the greater the hardness of the corresponding copolymer. Copyright © 2004 Society of Chemical Industry     

AB‐ and ABC‐type di‐ and triblock copolymers of poly[styrene‐block‐(ε‐caprolactone)] and poly[styrene‐block‐(ε‐caprolactone)‐block‐lactide]: synthesis,characterization and thermal studies

Polystyrene terminated with benzyl alcohol units was employed as a macroinitiator for ring‐opening polymerization of ε‐caprolactone and L ‐lactide to yield AB‐ and ABC‐type block copolymers. Even though there are many reports on the diblock copolymers of poly(styrene‐block‐lactide) and poly(styrene‐block‐lactone), this is the first report on the poly(styrene‐block‐lactone‐block‐lactide) triblock copolymer consisting of two semicrystalline and degradable segments. The triblock copolymers exhibited twin melting behavior in differential scanning calorimetry (DSC) analysis with thermal transitions corresponding to each of the lactone and lactide blocks. The block derived from ε‐caprolactone also showed crystallization transitions upon cooling from the melt. In the DSC analysis, one of the triblock copolymers showed an exothermic transition well above the melting temperature upon cooling. Thermogravimetric analysis of these block copolymers showed a two‐step degradation curve for the diblock copolymer and a three‐step degradation for the triblock copolymer with each of the degradation steps associated with each segment of the block copolymers. The present study shows that it is possible to make pure triblock copolymers with two semicrystalline segments which also consist of degradable blocks. Copyright © 2009 Society of Chemical Industry     

Effect of annealing on poly(urethane‐siloxane) copolymers

Poly(urethane‐siloxane) copolymers were prepared by copolymerization of OH‐terminated polydimethylsiloxane (PDMS), which was utilized as the soft segment, as well as 4,4′‐diphenylmethane diisocyanate (MDI) and 1,4‐butanediol (1,4‐BD), which were both hard segments. These copolymers exhibited almost complete phase separation between soft and hard segments, giving rise to a very simple material structure in this investigation. The thermal behavior of the amorphous hard segment of the copolymer with 62.3% hard‐segment content was examined by differential scanning calorimetry (DSC). Both the T₁ temperature and the magnitude of the T₁ endotherm increased linearly with the logarithmic annealing time at an annealing temperature of 100°C. The typical enthalpy of relaxation was attributed to the physical aging of the amorphous hard segment. The T₁ endotherm shifted to high temperature until it merged with the T₂ endotherm as the annealing temperature increased. Following annealing at 170°C for various periods, the DSC curves presented two endothermic regions. The first endotherm assigned as T₂ was the result of the enthalpy relaxation of the hard segment. The second endothermic peak (T₃) was caused by the hard‐segment crystal. The exothermic curves at an annealing temperature of above 150°C exhibited an exotherm caused by the T₃ microcrystalline growth. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5174–5183, 2006     

Synthesis and characterization of amphiphilic PMTFPS‐b‐PEO diblock copolymers

A series of new amphiphilic poly[methyl(3,3,3‐trifluoropropyl) siloxane]‐b‐poly(ethyleneoxide) (PMTFPS‐b‐PEO) diblock copolymers with different ratio of hydrophobic segment to hydrophilic segment were prepared by coupling reactions of end‐functional PMTFPS and PEO homopolymers. PMTFPS‐b‐PEO diblock copolymers synthesized were shown to be well defined and narrow molecular weight distributed by characterizations such as NMR, GPC, and FTIR. Additionally, the solution properties of these diblock copolymers were investigated using tensiometry and transmission electron microscopy. Interestingly, the critical micellization concentration increases with increasing length of hydrophobic chain. Transmission electron microscopy studies showed that PMTFPS‐b‐PEO diblock copolymers in water preferentially aggregated into vesicles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Copolymers based on poly(butylene terephthalate) and polycaprolactone‐block‐polydimethylsiloxane‐block‐polycaprolactone

A series of novel thermoplastic elastomers, based on poly(butylene terephthalate) (PBT) and polycaprolactone‐block‐polydimethylsiloxane‐block‐polycaprolactone (PCL‐PDMS‐PCL), with various mass fractions, were synthesized through melt polycondensation. In the synthesis of the poly(ester‐siloxane)s, the PCL blocks served as a compatibilizer for the non‐polar PDMS blocks and the polar comonomers dimethyl terephthalate and 1,4‐butanediol. The introduction of PCL‐PDMS‐PCL soft segments resulted in an improvement of the miscibility of the reaction mixture and therefore in higher molecular weight polymers. The content of hard PBT segments in the polymer chains was varied from 10 to 80 mass%. The degree of crystallinity of the poly(ester‐siloxane)s was determined using differential scanning calorimetry and wide‐angle X‐ray scattering. The introduction of PCL‐PDMS‐PCL soft segments into the polymer main chains reduced the crystallinity of the hard segments and altered related properties such as melting temperature and storage modulus, and also modified the surface properties. The thermal stability of the poly(ester‐siloxane)s was higher than that of the PBT homopolymer. The inclusion of the siloxane prepolymer with terminal PCL into the macromolecular chains increased the molecular weight of the copolymers, the homogeneity of the samples in terms of composition and structure and the thermal stability. It also resulted in mechanical properties which could be tailored. Copyright © 2010 Society of Chemical Industry     

Thermal and structural analysis of heparin–PEO–PDMS–PEO–heparin pentablock copolymers

ABCBA-type amphiphilic block copolymers comprising polydimethylsiloxane (PDMS), poly(ethylene oxide) (PEO), and heparin segments were synthesized by coupling reactions between end-functionalized oligomers. These multiblock copolymers were characterized to examine bulk properties using ¹H-NMR, FTIR, end-group analysis, and sulfur elemental analysis. Block copolymers were further characterized in bulk using differential scanning calorimetry and X-ray diffraction measurements. The PDMS glass transition remains unchanged with increasing PEO content, indicating coexistence of pure PDMS with mixed phases. Furthermore, endothermic melting of the block copolymers shifts to higher temperatures and becomes more intense with increasing PEO molecular weight. Additionally, the crystallinity of the PEO segment in the block copolymers increases with increasing PEO molecular weight. The PEO melting endotherm peak shifts from near 318 to 323 K with annealing. In the cooling thermogram, the block copolymers exhibit two crystallization exotherms, one near 303 K and the other near 193 K, attributed to PEO and PDMS recrystallization and nucleation, respectively. © 1994 John Wiley & Sons, Inc.     

Synthesis of polyurethane–imide (PU–imide) copolymers with different dianhydrides and their properties

This study reports the synthesis of polyurethane–imide (PU–imide) copolymers using 4,4′-diphenylmethane diisocyanate (MDI) polytetramethylene glycols (PTMGs) and different aromatic dianhydrides. Differential scanning calorimetry (DSC) results indicate that PU–imide copolymers had two phase structures containing four transition temperatures (T_gs, T_ms, T_gh and T_mh). However, only PU–imide copolymers were formed by soft PTMG(2000) segments possessing a T_ms (melting point of soft segment). When different aromatic dianhydrides were introduced into the backbone chain of the polyurethane, although the T_gs (glass transition temperature of the soft segment) of some of PU–imide copolymers did not change, the copolymers with long soft segments had low T_gs values. The T_gh (glass transition temperature of hard segment) values of PU–imide copolymers were higher than that of polyurethane (PU). In addition, the high hard segment content of PU–imide copolymer series also had an obvious T_mh (melting point of hard segment). According to thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTGA), the PU–imide copolymers had at least two stages of degradation. Although the T_di (initial temperature of degradation) depended on the hard segment content and the composition of hard segment, the different soft segment lengths did not obviously influence the T_di. However, PU–imide copolymers with a longer soft segment had a higher thermal stability in the degradation temperature range of middle weight loss (about T_d 5%–50%). However, beyond T_d 50% (50% weight loss at temperature of degradation), the temperature of degradation of PU–imide copolymers increased with increasing hard segment content. Mechanical properties revealed that the modulus and tensile strength of PU–imide copolymers surpassed those of PU. Wide angle X-ray diffraction patterns demonstrated that PU–imide copolymers are crystallizable. © 1999 Society of Chemical Industry     

Synthesis and characterization of multi‐block copolymers containing poly [(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] and poly(ethylene glycol)

Various problems, including high crystallinity, high melting temperature, poor thermal stability, hydrophobicity and brittleness, have impeded many practical applications of poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] (PHBV) as an environmentally friendly material and biomedical material. In the work reported here, multi‐block copolymers containing PHBV and poly(ethylene glycol) (PHBV‐b‐PEG) were synthesized with telechelic hydroxylated PHBV as a hard and hydrophobic segment, PEG as a soft and hydrophilic segment and 1,6‐hexamethylene diisocyanate as a coupling reagent to solve the problems mentioned above. PHBV and PEG blocks in PHBV‐b‐PEG formed separate crystalline phases with lower crystallinity levels and lower melting temperatures than those of phases formed in the precursors. The crystallite dimensions of the two blocks in PHBV‐b‐PEG were smaller than those of the corresponding precursors. Compared to values for the original PHBV, the maximum decomposition temperature of the PHBV block in PHBV‐b‐PEG was 16.0 °C higher and the water contact angle was 9° lower. In addition, the elongation at break was 2.8% for a pure PHBV fiber but 20.9% for a PHBV/PHBV‐b‐PEG fiber with a PHBV‐b‐PEG content of 30%. PHBV‐b‐PEGs can overcome some of the disadvantages of pure PHBV; it is possible that PHBV might be a good candidate for the formulation of environmentally friendly materials and biomedical materials. Copyright © 2010 Society of Chemical Industry     

Synthesis and characterization of degradable triarm low unsaturated poly(propylene oxide)‐block‐polylactide copolymers

A series of novel degradable triarm poly(propylene oxide)‐block‐polylactide (PPO‐b‐PLA) copolymers was synthesized by ring‐opening polymerization of L ‐lactide (LLA) or D ,L ‐lactide (DLLA) using low unsaturated PPO triols as macromolecular initiator. The chemical structures of the resulting copolymers were characterized by Fourier transform infrared (FTIR), gel permeation chromatography (GPC), and proton nuclear magnetic resonance (¹H‐NMR) spectroscopy. Combination of FTIR, GPC, and NMR results confirmed the formation of PPO‐b‐PLA copolymers. One glass transition was observed by differential scanning calorimetry (DSC), suggesting good miscibility between PPO and PLA segments in the copolymers. DSC and wide‐angle X‐ray diffraction demonstrated that PPO‐b‐PLLA copolymers were semicrystalline materials, and the crystallinity increased with increasing the PLLA content. In contrast, PPO‐b‐PDLLA copolymers were totally amorphous. The PPO‐b‐PLA copolymers exhibited improved thermal stability when compared with PPO polyols according to thermogravimetric analysis. The thermal degradation behavior of the copolymers depended on the composition. Polyurethane foams were prepared by crosslinking PPO and PPO‐b‐PLA copolymers using isocyanate. Alkaline degradation of the foams was investigated in 10 wt/vol % NaOH at 80°C. The results show that the novel PPO‐b‐PLA copolymers could be promising as degradable polymeric materials. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of semi‐crystalline poly(ε‐caprolactone) and non‐crystalline polylactide blocks on the thermal properties of polydimethylsiloxane‐based block copolymers

Poly(A)‐block‐poly(B), poly(A)‐block‐poly(B)‐block‐poly(A) and B(A)₂ block copolymers were prepared through coordinated anionic ring‐opening polymerization of ε‐caprolactone (CL) and lactic acid (LA) using hydroxy‐terminated polydimethylsiloxane (PDMS) as initiator. A wide range of well‐defined combinations of PDMS‐block‐PCL and PDMS‐block‐PLA diblock copolymers, PCL‐block‐PDMS‐block‐PCL and PLA‐block‐PDMS‐block‐PLA triblock copolymers and star‐PDMS(PCL)₂ copolymers were thus obtained. The number‐average molar masses and the structure of the synthesized block copolymers were identified using various analytical techniques. The thermal properties of these copolymers were established using differential scanning calorimetry. Considering PDMS‐block‐PCL copolymers, the results demonstrate the complex effect of polymer architecture and PCL block length on the ability of the PDMS block to crystallize or not. In the case of diblock copolymers, crystallization of PCL blocks originated from stacking of adjacent chains inducing the extension of the PDMS block that can easily crystallize. In the case of star copolymers, the same tendency as in triblock copolymers is observed, showing a limited crystallization of PDMS when the length of the PCL block increases. In the case of PDMS‐block‐PLA copolymers, melting and crystallization transitions of the PLA block are never observed. Considering the diblock copolymers, PDMS sequences have the ability to crystallize. © 2019 Society of Chemical Industry