Effect of deformation on the surface composition of multicomponent polymers. II. Blends of polydimethylsiloxane–polysulfone block copolymers in polychloroprene

The effect of uniaxial stretching on the surface composition of dilute blends of polydimethylsiloxane/polysulfone 2500/44,000 and 2500/3500 block copolymers in polychloroprene is studied using X-ray photoelectron spectroscopy. The surface of the initial (unstretched) blends is found to be covered by a discontinuous copolymer overlayer with a thickness greater than the XPS sampling depth. The stretching leads to a substantial drop in the extent of the copolymer surface segregation. For the 2500/3500 block copolymer, the dependence of the surface composition of the blends on the stretching degree is well described by a homogeneous deformation model, whereas for blends of the 2500/44,000 copolymer, the stretching of the copolymer overlayer lags noticeably behind that of the polychloroprene matrix. In the blends of the 2500/3500 copolymer, the stretching has practically no effect on the distribution of the copolymer components in the near-surface region. By contrast, the 2500/44,000 copolymer shows a substantial surface depletion of siloxane with stretching. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2349–2356, 1998     

The study of surface segregation and the formation of gradient domain structure at the blend of poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers and acrylate adhesive copolymers

The effect of siloxane chain length on surface segregation of poly(methyl methacrylate)‐grafted poly(dimethyl siloxane) (PMMA‐g‐PDMS)/poly(2‐ethylhexyl acrylate‐co‐acrylic acid‐co‐vinyl acetate) [P(2EHA‐AA‐VAc)] blends was investigated. The blends of PMMA‐g‐PDMS with P(2EHA‐AA‐VAc) showed surface segregations of PDMS components. The surface enrichments of PDMS in the blends depended significantly on the PDMS chain length. Also, this blend showed the gradient domain structure. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 375–380, 2003     

Compositional variations in cast films of blends of copolymers of siloxanes and poly(methyl methacrylate) determined by energy dispersive spectroscopy and X-ray image analysis

Films cast on gold surfaces from 3% methylene chloride solutions of syndiotactic poly(methyl methacrylate) (PMMA) (M_n = 23,000) and random copolymers of PMMA and 4-(methacryloyloxybutyl) pentamethyldisiloxane (MBPD) (M_n = 40,000) are all heterogeneous with visible phase separation occurring over most of the compositional range. Energy dispersive spectroscopy (EDS) shows that for PMMA blended with the copolymers there is an excess of silicon, ranging from 1.9 wt% to 9.7 wt%, in the surface exposed to air during casting, while the lower surface exposed to the gold is depleted in silicon. X-Ray mapping and image analysis show that for blends containing 50% or less of siloxane copolymer the upper surface is composed of large siloxane rich domains in a PMMA matrix while the lower surface is composed of much smaller and less abundant siloxane domains in a PMMA matrix. In addition, the siloxane domains of the upper surface contain small PMMA domains. For blends with a greater siloxane content, the upper surface is composed of a siloxane matrix while the lower surface remains PMMA rich.     

Surface modification of poly(vinyl chloride) with poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers

X-ray photoelectron spectroscopy is used to study the surface segregation of siloxane in dilute blends of poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers in poly(vinyl chloride)(PVC). The graft copolymers are found to be extremely efficient surface modifiers, which form, when added in amounts of 0.5% or more, a continuous siloxane overlayer on the surface of PVC. © 1995 John Wiley & Sons, Inc.     

Syntheses of poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers and their surface enrichment of their blend with acrylate adhesive copolymers

Several types of poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers (PMMA‐g‐PDMS) were synthesized using macromonomer technology. Three types of PMMA‐g‐PDMS with different PDMS chain length were obtained. The effect of siloxane chain length on surface segregation of PMMA‐g‐PDMS/poly(2‐ethylhexyl acrylate‐co‐acrylic acid‐co‐vinyl acetate)[P(2EHA‐AA‐VAc)] blends was investigated. The blends of PMMA‐g‐PDMS with P(2EHA‐AA‐VAc) showed surface segregations of PDMS components. The surface enrichments of PDMS in the blends depended on the PDMS chain length, significantly. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1736–1740, 2002     

Surface behavior of dilute blends of poly(vinyl chloride) with siloxane–urethane–ethyleneoxide oligomers

X-ray photoelectron spectroscopy is used to study the surface segregation of siloxane in blends of poly(vinyl chloride) with siloxane–urethane–ethyleneoxide oligomers. At high concentration of the oligomeric additive, the surface segregation of siloxane in the blends strongly depends on the molecular architecture of the additive: the segregation is much higher when the siloxane blocks are at the ends of the oligomeric chains. At low additive concentrations, the surface segregation of siloxane is governed solely by the siloxane concentration in the bulk. © 1995 John Wiley & Sons, Inc.     

Effect of substrate on gradient domain morphology formed in acrylate copolymer/fluoro-copolymer blends

The effect of the substrate on the gradient domain morphology was investigated for immiscible blends of poly(2-ethylhexyl acrylate-co-acrylicacid-co-vinylacetate) [P(2EHA-AA-VAc)] and poly(vinylidene fluoride-co-hexafluoro acetone) [P(VDF-HFA)]. The blends were prepared on substrates of poly(dimethyl siloxane) (PDMS) coated on a liner and of poly(tetrafluoro ethylene) (PTFE) from a THF solution by coating. The chemical compositions and the cross-sectional morphology of the surface (surface in contact with air) and bottom (surface in contact with substrate) sides were examined by attenuated total reflection Fourier transform infrared spectroscopy and scanning electron microscopy. The P(2EHA-AA-VAc)/P(VDF-HFA) (50/50), (30/70) blends prepared on PDMS revealed a gradient domain morphology, whereas the (50/50) and (30/70) blends prepared on PTFE formed a sea-island type of phase separation structure. On the other hand, when the P(2EHA-AA-VAc)/P(VDF-HFA) (70/30) blend was prepared on PTFE, P(2EHA-AA-VAc) and P(VDF-HFA) components segregated at the surface and the bottom, respectively. We concluded that the affinity between P(VDF-HFA) and the substrates strongly influenced the formation of the gradient domain morphology and the surface segregation of P(2EHA-AA-VAc).     

Intermolecular interaction and conformation in poly(ether ether ketone)/poly(ether imide) blends — An infrared spectroscopic investigation

The intermolecular interaction and the conformation in miscible blends of poly(ether ether ketone) (PEEK) and poly(ether imide) (PEI) have been investigated by Fourier-transform infrared (FTIR) spectroscopy. The intensity of the C=O out-of-phase stretching (1725 cm^–1) of PEI shows a minimum at 70 wt% PEI, whereas that of the C=O in-phase stretching (1778 cm^–1) is not perturbed by blending. These intensity variations have been attributed to the effect of blending on the coplanarity of the two imide rings bridged by the phenylene group. Change in coplanarity of these two imide rings alters the intensity of the C=O out-of-phase stretching, but it can not affect the intensity of the C=O in-phase stretching. When the two imide rings are perpendicular to each other, the intensity of the C=O out-of-phase stretching is shown to reach the minimum, corresponding to the observation at 70 wt% PEI. The difference spectra (blend - PEEK - PEI) reveal that the bands associated with the diphenyl ether groups in PEEK are modified by blending with PEI. It is proposed that the favorable interaction takes place between the oxygen lone-pair electrons of the ether group in PEEK and the electron-deficient imide rings in PEI.     

Surface segregation of siloxane containing component in polysiloxane‐block‐polyimide and s‐BPDA/ODA polyimide blends

Surface segregation in polymer blend systems between 3,3′,4,4′‐biphenyltetracarboxylic dianhydride/4,4′‐diaminodiphenyl ether (s‐BPDA/ODA) polyimide and block copolymer based on polysiloxane‐block‐polyimide (SPI) has been investigated. These polyimide blends, having various compositions of the SPI, were processed by a solution casting method. The glass substrate used in the film‐casting process shows significant effect on the migration of surface segregated species to enrich the air‐exposed surface, whereas the more polar s‐BPDA/ODA tends to remain close to the polar glass substrate. X‐ray photoelectron spectroscopy reveals that even at low SPI concentration, the siloxane moieties in the block copolymer tend to segregate into the air side surface. Contact angle measurement evidently indicates an enrichment of the hydrophobic siloxane fraction on the blend film surface. The average water contact angle of glass side surface is 77°C whereas that of the air side is about 102°C in every blend ratio. This behavior confirms the surface segregation phase separation in these polymer blends. Finally, the surface morphology observed by atomic force microscopy also suggests segregation type of phase separation in these blend systems. POLYM. ENG. SCI., 47:489–498, 2007. © 2007 Society of Plastics Engineers.     

增容剂对PP/PET原位微纤化共混物的影响

通过"熔融挤出-热拉伸-淬冷"的方法制备了原位微纤化共混物。采用扫描电镜、差示扫描量热仪和力学性能测试等方法研究了增容剂PP-g-GMA含量对共混物微观形态、力学性能和结晶性能的影响。结果表明,增容剂的加入可明显提高两相相容性,改善界面效果,明显降低拉伸前初始粒子的尺寸,但同时使拉伸后形成的微纤呈现一定的损坏,长径比有所降低。增容剂可以明显改善微纤化共混物力学性能,当其含量为2 %（质量分数,下同）时拉伸强度比未增容试样提高了11.0 %,弯曲强度都提高了11.3 %;当其含量为6 %时冲击强度也比未增容共混物提高了34.5 %。此外,PET微纤对PP有很好的异相成核作用,使其结晶温度提高了16.3 ℃,结晶时间为纯PP的32 %左右,而增容剂的加入使共混物中PP的结晶时间延长。     

Preparative fractionation and characterization of polycarbonate/eugenol-siloxane copolymers

Bisphenol-A polycarbonate/eugenol-siloxane copolymers were fractionated at the preparative scale by the continuous polymer fractionation (CPF) technique. It is the first example of copolymer fractionation by CPF. The distribution of siloxane species across the fractions was assessed for copolymers differing in initial siloxane concentration and block length. On- and off-line combinations of size exclusion chromatography and infrared spectroscopy were used to analyze chemical composition (CC) of the unfractionated samples across the molecular weight distribution enabling comparison with the fractions. A polycarbonate-siloxane copolymer containing 10 wt% of very short siloxane blocks (dp=2) was fractionated solely according to molecular weight (MW). By contrast, a copolymer containing 5 wt% siloxane blocks with a larger degree of polymerization (dp=23) was fractionated according to MW, as well as to CC. This ‘chemical drift’ effect for the larger siloxane block length can be ascribed to large solubility differences of low MW chains, which drastically vary in composition according to the (small) number of siloxane blocks they contain.     

Effect of thermal history on the molecular orientation in polystyrene/poly(vinyl methyl ether) blends

The effect of thermal history on the orientation and relaxation behavior of blends of polystyrene with poly(vinyl methyl ether) (PS/PVME) has been studied using polarization modulation infrared linear dichroism (PM-IRLD) and differential scanning calorimetry (DSC). DSC shows that miscible PS/PVME blends containing 70% of PS can be physically aged at temperatures above their mean glass transition temperature (T_g). PM-IRLD measurements reveal that both components become more oriented upon stretching at 51 °C (8 °C above T_g) if the sample is aged at the deformation temperature prior to stretching. Room-temperature aging can also lead to an increased orientation if the heating time at 51 °C is kept short. Moreover, PS and PVME develop a larger orientation in phase-separated blends than in miscible ones, and their relaxation is hindered. The results have been interpreted considering the morphology of the samples, including the presence of concentration fluctuations in miscible blends, and the effect of the local environment on the rigidity of the chains.     

Role of poly(lactic acid) in the phase transition of poly(vinylidene fluoride) under uniaxial stretching

The effect of poly (lactic acid) (PLA) on the crystalline phase transition of poly (vinylidene fluoride) (PVDF) from α‐ to β‐phase under uniaxial stretching for immiscible PVDF/ PLA blends was investigated. The typical sea‐island structure in the blends was found to facilitate the necking of PVDF and the transition from α‐ to β‐phase due to the local stress distribution during stretching. The crystalline phase transition of PVDF in the blends is temperature‐dependent and is affected by the content of PLA. The highest content of β‐phase, F(β), was achieved in the samples stretched at 60°C, while the effect of PLA content on the crystalline phase transition of PVDF is more complex. F(β) increases slightly when the sample with a PLA content no more than 15 wt % is stretched at 60, 80, and 100°C, and decreases sharply for the sample containing 20 wt % PLA; in addition, the sample containing 10 wt % PLA exhibits the highest F(β) no matter what the stretching temperature is. The mechanism of the crystalline phase transition of PVDF during the stretching is interpreted from energy barrier of the transition from α‐ to β‐phase and the morphological structures in the blends. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Unique Crystallization Behavior of Poly(L-lactic acid) Nucleated by Stereocomplex with Different Fine Structure

Effect of the addition of poly(D-lactic acid) (PDLA) as stereocomplex (SC) on crystallization behavior of poly(L-lactic acid) (PLLA) had been systemically investigated. The result indicated that the inclusion of PDLA with higher MW into PLLA exhibited lower t _1/2 and showed accelerated crystallization behavior. Meanwhile, SC formed in blends with higher MW of PDLA exhibited enhanced nucleation activity. In combination with both DSC and WAXD analysis, it was believed that nucleation process was more related to the crystalline size of SC. The result in this study would provide guidance for the application of SC as nucleating agent for the PLA-based products.     

Effect of a chain extender on the rheological and mechanical properties of biodegradable poly(lactic acid)/poly[(butylene succinate)‐co‐adipate] blends

Biodegradable polymer blends based on poly(lactic acid) (PLA) and poly[(butylene succinate)‐co‐adipate] (PBSA) were prepared with a laboratory internal mixer. An epoxy‐based, multifunctional chain extender was used to enhance the melt strength of the blends. The morphology of the blends was observed with field emission scanning electron microscopy. The elongational viscosities of the blends, with and without chain extender, were measured with a Sentmanat extensional rheometer universal testing platform. The blends with chain extender exhibited strong strain‐hardening behavior, whereas the blends without chain extender exhibited only weak strain‐hardening behavior. Measurements of the linear viscoelastic properties of the melts suggested that the chain extender promoted the development of chain branching. The results show that PBSA contributed to significant improvements in the ductility of the PLA/PBSA blends, whereas the chain extender did not have a significant effect on the elastic modulus and strain at break of the blends. The combined blending of PLA with PBSA and the incorporation of the chain extender imparted both ductility and melt strength to the system. Thus, such an approach yields a system with enhanced performance and processability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Surface Energy and Thermal Stability Studies of Poly(dimethyl siloxane)–Poly(alkyl(meth)acrylate) Copolymers

The correlation between the surface energy and thermal stability of polymers plays an important role in engineering of plastic materials. In this work, microstructural characteristics of copolymers of poly(dimethyl siloxane) with benzyl methacrylate, ethyl methacrylate, and methyl acrylate are correlated with their surface energy and thermal stability. The poly(dimethyl siloxane) segments in the copolymer chains affected the hydrophobic behavior. The surface energy of the synthesized copolymers decreased by increasing segments of alkyl methacrylates. The thermal stability of copolymers suggesting that heat resistance of poly(dimethyl siloxane) copolymers used in this correlation can be improved by adjusting the units of alkyl methacrylates in copolymers.     

Effect of the shape of dispersed particles on the thermal and mechanical properties of biomass polymer blends composed of poly(L‐lactide) and poly(butylene succinate)

The structure and properties of binary blends composed of poly(lactic acid) (PLA) and fibrous poly(butylene succinate) (PBS), which were prepared by an uniaxial stretching operation in the molten state, were studied and compared with those of blends having spherical particles of PBS in a continuous PLA phase. We found from electron microscope observation that PBS nanofibers with a large aspect ratio were generated in the stretched samples. Enlargement of the surface area of the PBS particles, which showed nucleating ability for PLA, led to a high degree of crystallization and enhanced the cold crystallization in the heating process. Moreover, the PBS fibers in the stretched samples had a dominant effect on the mechanical properties in the point range between the glass‐transition temperature of PLA and the melting temperature of PBS. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Surface behavior of blends of siloxane and siloxane-containing copolymers in poly(vinyl chloride)

X-ray photoelectron spectroscopy is used to reveal surface/bulk compositional relationships in blends of polydimethylsiloxane (PDMS) and PDMS/polycarbonate block copolymers in poly(vinyl chloride) (PVC). It is shown that the surface of PVC can be enriched in siloxane up to 60 at. % PDMS without visible indications of phase separation.     

Mixed macrodiol‐based siloxane polyurethanes: Effect of the comacrodiol structure on properties and morphology

Two series of polyurethanes were prepared to investigate the effect of comacrodiol structure on properties and morphology of polyurethanes based on the siloxane macrodiol, α,ω‐bis(6‐hydroxyethoxypropyl) polydimethylsiloxane (PDMS). All polyurethanes contained a 40 wt % hard segment derived from 4,4′‐methylenediphenyl diisocyanate (MDI) and 1,4‐butanediol (BDO), and were prepared by a two‐step, uncatalyzed bulk polymerization. The soft segments were based on an 80/20 mixture of PDMS (MW 967) and a comacrodiol (MW 700), selected from a series of polyethers and polycarbonates. The polyether series included poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), poly(tetramethylene oxide) (PTMO), poly(hexamethylene oxide), and poly(decamethylene oxide) (PDMO), whereas the polycarbonate series included poly (hexamethylene carbonate) diol (PHCD), poly [bis(4‐hydroxybutyl)‐tetramethyldisiloxy carbonate] diol (PSCD), and poly [hexamethylene‐co‐bis(4‐hydroxybutyl)‐tetramethyldisiloxy carbonate] diol (COPD). Polyurethanes were characterized by size exclusion chromatography, tensile testing, differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA). The results clearly demonstrated that the structure of the comacrodiol influenced the properties and morphology of siloxane‐based polyurethanes. All comacrodiols, except PEO, improved the UTS of the polyurethane; PHMO and PTMO were the best polyether comacrodiols, while PSCD was the best polycarbonate comacrodiol. Incorporation of the comacrodiol made polyurethanes more elastomeric with low modulus, but the effect was less significant with polycarbonate comacrodiols. DSC and DMTA results strongly supported that the major morphological change associated with incorporation of a comacrodiol was the significant increase in the interfacial regions, largely through the compatibilization with the hard segment. The extent of compatibilization varied with the comacrodiol structure; hydrophilic polyethers such as PEO were the most compatible, and consequently, had poor mechanical strength. Among the polyethers, PHMO was the best, having an appropriate level of compatibility with the hard segment for substantial improvement in mechanical properties. Siloxy carbonate comacrodiol PSCD was the best among the polycarbonates. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1071–1082, 2000     

Electrocapillary wave studies of different poly(dimethyl siloxane)s

The monolayer behavior of different end-functionalized poly(dimethyl siloxane)s (PDMSs) and a block copolymer, poly(dimethyl siloxane-co-ethylene oxide) (PDMS-co-EO) spread on an oligomeric poly(ethylene glycol) (PEG) substrates, were studied by means of electrocapillary wave diffraction (ECWD). Over a relatively small temperature range (40–70°C), the damping constant was more dependent on temperature than on the wave vector. Different surface layer properties were observed for two PDMS: one terminated with a methyl group (PDMS-CH₃) and the one terminated with a hydroxy group (PDMS-OH). PDMS-OH showed a larger reduction in surface tension compared to PDMS-CH₃ because of a higher interfacial affinity with PEG, which indicated that its monolayer surface activity was weaker. A lower surface elasticity of PDMS-OH than that of PDMS-CH₃ supported that conclusion. The block copolymer showed no surface activity, since the short siloxane moiety did not repel the strong interaction between PEG and the ethylene oxide.