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1.
Fábio A. Bonk Stefano Caldarelli Trang Phan Denis Bertin Eduardo R. Deazevedo Gerson Luiz Mantovani Tito J. Bonagamba Tomás S. Plivelic Iris L. Torriani 《Journal of Polymer Science.Polymer Physics》2010,48(1):55-64
The microphase structure of a series of polystyrene‐b‐polyethylene oxide‐b‐polystyrene (SEOS) triblock copolymers with different compositions and molecular weights has been studied by solid‐state NMR, DSC, wide and small angle X‐ray scattering (WAXS and SAXS). WAXS and DSC measurements were used to detect the presence of crystalline domains of polyethylene‐oxide (PEO) blocks at room temperature as a function of the copolymer chemical composition. Furthermore, DSC experiments allowed the determination of the melting temperatures of the crystalline part of the PEO blocks. SAXS measurements, performed above and below the melting temperature of the PEO blocks, revealed the formation of periodic structures, but the absence or the weakness of high order reflections peaks did not allow a clear assessment of the morphological structure of the copolymers. This information was inferred by combining the results obtained by SAXS and 1H NMR spin diffusion experiments, which also provided an estimation of the size of the dispersed phases of the nanostructured copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 55–64, 2010 相似文献
2.
Firmin Moingeon Yan Rong Wu Lorena Eugenia Cadena‐Sánchez Mario Gauthier 《Journal of polymer science. Part A, Polymer chemistry》2012,50(9):1819-1826
The synthesis of arborescent styrenic homopolymers and copolymers was achieved by anionic polymerization and grafting. Styrene and p‐(3‐butenyl)styrene were first copolymerized using sec‐butyllithium in toluene, to generate a linear copolymer with a weight‐average molecular weight Mw = 4000 and Mw/Mn = 1.05. The pendant double bonds of the copolymer were then epoxidized with m‐chloroperbenzoic acid. A comb‐branched (or arborescent generation G0) copolymer was obtained by coupling the epoxidized substrate with living styrene‐p‐(3‐butenyl)styrene copolymer chains with Mw ≈ 5000 in a toluene/tetrahydrofuran mixture. Further cycles of epoxidation and coupling reactions while maintaining Mw ≈ 5000 for the side chains yielded arborescent copolymers of generations G1–G3. A series of arborescent styrene homopolymers was also obtained by grafting Mw ≈ 5000 polystyrene side chains onto the linear and G0–G2 copolymer substrates. Size exclusion chromatography measurements showed that the graft polymers have low polydispersity indices (Mw/Mn = 1.02–1.15) and molecular weights increasing geometrically over successive generations. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
3.
Ging-Ho Hsiue Wen-Kuei Huang Wei-Hsin Hou 《Journal of polymer science. Part A, Polymer chemistry》1989,27(12):4119-4128
The morphological and dynamic properties of epoxidized styrene–butadiene–styrene block copolymers were studied and compared with their parent styrene–butadiene–styrene block copolymer (SBS). Two peaks were observed in the mechanical loss (tan δ) curve which can be attributed to segmental motion of epoxidized polybutadiene (EPPB) and polystyrene. Analysis by DSC thermograms also showed the linear increase of glass transition temperature for EPPB domain with the epoxy group content. Phase separated structures of epoxidized SBS as observed by TEM suggests a considerable degree of mixing occurred between phases after 80 mol % of the double bonds in SBS were epoxidized. The interfacial region displays a third peak and causes much steeper drop in modulus at higher temperature than Tg of EPPB. Parallel dielectric relaxation measurements were also made in the frequency range of 30 Hz–1 KHz as a function of temperature. In each dielectric constant (?′) curve, there is a maximum near the Tg of EPPB determined from the dielectric loss tangent curve. The shift in Tg of EPPB versus epoxy group content was consistent with that measured by the thermal and dynamic mechanic analysis. These findings indicated an 8°C shift in glass transition temperature as the epoxy group content in EPPB increased 10%. 相似文献
4.
Kanehiro Nakamura Ryuichi Endo Masatami Takeda 《Journal of Polymer Science.Polymer Physics》1977,15(12):2095-2101
Molecular motions of hydrophobic–hydrophilic water-soluble block copolymers in solution were investigated by high-resolution proton magnetic resonance (NMR). Samples studied include block copolymers of polystyrene–poly(ethylene oxide), polybutadiene–poly(ethylene oxide), and poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide). NMR measurements were carried out varying molecular weight, temperature, and solvent composition. For AB copolymers of polystyrene and poly(ethylene oxide), two peaks caused by the phenyl protons of low-molecular-weight (M?n = 3,300) copolymer were clearly resolved in D2O at 100°C, but the phenyl proton peaks of high-molecular-weight (M?n = 13,500 and 36,000) copolymers were too broad to observe in the same solvent, even at 100°C. It is concluded that polystyrene blocks are more mobile in low-molecular-weight copolymer in water than in high-molecular-weight copolymer in the same solvent because the molecular weight of the polystyrene block of the low-molecular-weight copolymer is itself small. In the mixed solvent D2O and deuterated tetrahydrofuran (THF-d8), two peaks caused by the phenyl protons of the high-molecular-weight (M?n = 36,000) copolymer were clearly resolved at 67°C. It is thought that the molecular motions of the polystyrene blocks are activated by the interaction between these blocks and THF in the mixed solvent. 相似文献
5.
J. M. G. Cowie Guangxian Li R. Ferguson I. J. McEwen 《Journal of Polymer Science.Polymer Physics》1992,30(12):1351-1358
The miscibilities of ternary copolymer blends prepared from poly(styrene-stat-acrylonitrile), poly(styrene-stat-methyl methacrylate), and poly(methyl methacrylate-stat-acrylonitrile) were predicted by calculating the interaction parameter, χblend, for various blend combinations, from the corresponding binary segmental interaction parameters estimated from previous work. Binodal and spinodal curves were calculated using the Flory-Huggins theory and it was observed that the most accurate estimate of the boundary between miscible and immiscible blends was given by the spinodal. It has also been demonstrated that in some of the ternary blends with fixed copolymer compositions the miscibility of the blend can be altered by changing the ratio of the three components in the mixture. Conditions for miscibility in this ternary system, and possibly a general feature of all such systems, are (a) that at least two of the binary interaction parameters χij are less than the critical value χcrit, while the third should not be too much larger, that is, one of the copolymers may act as a compatibilizer for the other two copolymers, (b) that the difference Δχ = /χ12 ? χ13/ is small. © 1992 John Wiley & Sons, Inc. 相似文献
6.
V. B. F. Mathot R. L. Scherrenberg M. F. J. Pijpers W. Bras 《Journal of Thermal Analysis and Calorimetry》1996,46(3-4):681-718
Ethylene-propylene (EP) and ethylene-octene (EO) copolymers polymerized with the aid of homogeneous vanadium and metallocene catalysts were compared by DSC and time-resolved simultaneous SAXS-WAXS-DSC at scanning rates of 10 and 20°C min?1 using synchrotron radiation. An EP copolymer with a density of 896 kg m?3 (about 89 mol % ethylene) after compression moulding gave orthorhombic WAXS reflections. The crystallinity as a function of temperature [w c (T)] calculated from these reflections using the two-phase model was in good agreement withw c (T) calculated fromc p measurements using DSC. Thec p measurements also enabled calculation of the baselinec p and the excessc p. The SAXS measurements revealed a strong change in the long period in cooling and in heating. The SAXS invariant as a function of temperature showed a maximum in both cooling and heating, which could be explained from the opposing influences of the crystallinity and the electron density difference between the two phases. Two EO copolymers with densities of about 871 kg m?3 (about 87 mol% ethylene) no longer showed any clear WAXS reflections, although DSC and SAXS measurements showed that these copolymers did crystallize. The similarity between the results led to the conclusion that the copolymers, though based on different catalyst systems — vanadium and metallocene — did not have strongly different sets of propagation probabilities of chain growth during polymerization. On the basis of a Monte Carlo simulation model of crystallization and morphology, based on detailed knowledge of the microchain structure, the difference between WAXS on the one hand and DSC and SAXS on the other could be explained as being due to loosely packed crystallized ethylene sequences in clusters. These do cause the density and the electron density of the cluster to increase (which is measurable by SAXS) and the enthalpy to decrease (which is measurable by DSC) but the clusters are too small and/or too imperfect to give constructive interference in the case of WAXS. Of an EP copolymer with an even lower ethylene content (about 69 mol %), the crystallization and melting processes could still be readily measured by DSC and SAXS, which proves that these techniques are eminently suitable for investigating the crystallization and melting behaviour of the copolymers studied. 相似文献
7.
Momoka Watanabe Yusuke Asai Atsushi Takano Yushu Matsushita 《Journal of Polymer Science.Polymer Physics》2019,57(14):952-960
Microphase‐separated structures of a series of AB6 block‐graft copolymers were studied by TEM and SAXS. Ten copolymers with the same polystyrene (S) backbone and six polyisoprene (I) grafts on the average but with different graft chain lengths were carefully synthesized by living anionic polymerization, covering the range 0.21 ≤ ?S ≤ 0.90, where ?S denotes polystyrene compositions. From TEM observation of the AB6 block‐graft copolymers, it turns out to be clear that they show four microphase‐separated structures, S‐spheres, S‐cylinders(S‐prisms), alternative lamellae, and I‐cylinders. Among them, for example, the samples with 0.54 ≤ ?S ≤ 0.58 shows prism structures whose cross sections of the S domains are close to hexagons, not circles, due to packing frustration of grafts. Composition dependence of morphologies of the present AB6 block‐graft copolymers reveals their phase diagram is extremely asymmetric with respect to ?S = 0.5. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 952–960 相似文献
8.
Films of polystyrene–polybutadiene–polystyrene (PS/PB/PS) triblock copolymer and polystyrene-poly(ethylene/propylene) (PS/PEP) diblock copolymer were cast from toluene solutions subjected to hydrodynamic flow at room temperature using a device based on a novel casting method we term ‘roll-casting.’ Polymer solutions were rolled between two corotating eccentric cylinders while at the same time the solvent was removed at a controlled rate. As the solvent evaporated, the block copolymers microphase separated into globally oriented structures. A discussion of the flow field that develops during roll-casting is presented and specific attention is given to the importance of the shear and elongation rates present. For the triblock and diblock, respectively, the processed structures consisted of polystyrene cylinders assembled on a hexagonal lattice in a polybutadiene matrix, and unidirectional lamellae of alternating polystyrene and polyethylene/propylene. Small-angle x-ray scattering (SAXS) and transmission electron microscopy (TEM) indicated the near single-crystal structure both types of films. SAXS also showed the styrene cylinders and the alternating lamellae to be packed closer together in roll-cast films than in simple quiescently cast films. A molecular orientation mechanism is proposed to describe both these results as well as the changes in packing and in macroscopic sample dimensions measured after complete solvent evaporation and after sample annealing. © 1993 John Wiley & Sons, Inc. 相似文献
9.
Kanehiro Nakamura Ryuichi Endo Masatami Takeda 《Journal of Polymer Science.Polymer Physics》1977,15(12):2087-2093
Interactions of water-soluble AB block copolymers of polystyrene and poly(ethylene oxide) with sodium lauryl sulfate (SLS) in aqueous solution were investigated by high-resolution proton magnetic resonance (NMR). The viscosity in aqueous SLS solution was also measured. From the NMR results in D2O, it appears that molecular motions of the polystyrene blocks of the copolymer in aqueous solution are activated by interaction between the polystyrene blocks and the added SLS. From solution viscosity, on the other hand, it is apparent that a complex is formed between the copolymer and SLS and that it exhibits typical polyelectrolyte properties. The polyelectrolyte character is attributable largely to intrachain repulsions between like charges of the SLS anions adsorbed on the poly(ethylene oxide) blocks of the copolymers since the polystyrene blocks are insoluble in water and the styrene content is less than 10%. 相似文献
10.
Nikos Hadjichristidis Yiannis Poulos Apostolus Avgeropoulos 《Macromolecular Symposia》1998,132(1):207-220
The synthesis of non linear block copolymers of the type (BA)2B (3-miktoarm star copolymer), (BA)3B (4-miktoarm star copolymer), (BA)3B(AB)3 (super H-shaped), B2AB2 (H-shaped) and (B,A)A(B,A) (π-shaped), where A is polyisoprene 1,4 and B is polystyrene was performed using anionic polymerization techniques and suitable chlorosilane chemistry. Characterization data showed that the samples are molecularly and compositionally homogeneous. TEM, SAXS and SANS were used to study the microphase behavior of the copolymers. For all samples, the results were analyzed in the frame of the theoretical predictions given by Milner and taking into account the results from previous studies on the A2B and A3B miktoarm star copolymers. 相似文献
11.
S. Cimmino F. E. Karasz W. J. MacKnight 《Journal of Polymer Science.Polymer Physics》1992,30(1):49-59
Miscibility in blends of random copolymers of o-chlorostyrene and p-chlorostyrene [P(oClSy-co-pClS1-y)] with 8 atactic polystyrene (aPS) fractions has been studied at temperatures ranging from 150°C to 300°C. Miscibility windows whose size depends on the molecular weight of the PS and on the copolymer composition, y, were observed for each blend. From these data, the temperature dependence of the three segmental interaction parameters required to describe this system were obtained. 相似文献
12.
The morphology of crystalline end-block copolymers of poly(thiacyclobutane-b-isoprene-b-thiacyclobutane) (TCB–I–TCB) was studied by optical microscopy, electron microscopy, and small-angle x-ray scattering (SAXS). A spherulitic texture was observed for both the TCB homopolymer and the TCB–I–TCB block copolymers. Well-defined phases arranged in an ordered structure exist when the films are cast above the melting temperature of the crystalline end blocks. The dimensions and the arrangements of the domains have been derived from both SAXS and electron microscope measurements. The deformation mechanism of the 41% end-block copolymer sample was also examined by a combination of SAXS and stress–strain studies. It was found that the interdomain spacing increased along the stretching direction as the extension ratio was increased. The morphology changes from hexagonally packed cylinders to rowtype cylinders upon the application of stress. 相似文献
13.
Chun‐Jie Chang Yi‐Huan Lee Chi‐Ju Chiang Yu‐Ping Lee Hao‐Ching Chien Wen‐Pin Shih Yao‐Yi Cheng Chi‐An Dai Chia‐Hwa Chang 《Journal of Polymer Science.Polymer Physics》2010,48(16):1834-1846
In this study, we investigate the effect of random copolymer additives on the interfacial profile, the lateral phase separation morphology, and the interfacial fracture toughness (Gc) between two immiscible polymers. The interface between polystyrene (PS)/poly(methyl methacrylate) (PMMA) was reinforced with a random copolymer mixture when two or more PSf ‐r‐PMMA1‐f random copolymers with different volume fraction, f, were blended. For short annealing time (<3 h), the random copolymer mixture exhibits a disordered and large domain structure (>1 lm) from which crazes can be extensively initiated and developed, leading to a large interfacial fracture energy. With increasing annealing time, the random copolymer mixture self‐organizes as multiple layers, with the composition that changes gradually from PS‐rich layers to PMMA‐rich layers across the interface, leading to a large interfacial width. However, within each layer, the random copolymer mixture microphase separates laterally into smaller domains (<200 nm). We found that the microphase‐separated domains with nanometer‐sized structure significantly affect the stability of craze fibrils that can be initiated and widened at the interface, leading to a decrease in the fracture energy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1834–1846, 2010 相似文献
14.
Patric Jannasch Helen Hassander Bengt Wessln 《Journal of Polymer Science.Polymer Physics》1996,34(7):1289-1299
Macro- and microphase separation of compatibilizing graft copolymers in melt-mixed polystyrene/polyamide-6 blends was studied by transmission electron microscopy and thermal analysis. Three different graft copolymers with main chains of polystyrene and side chains of poly(ethylene oxide) were used as additives at various concentrations. The polyamide-6 domain sizes decreased with increasing amounts of compatibilizing graft copolymers in the blends up to a saturation concentration, after which no further reduction was noted. Macrophase separation of the graft copolymers into discrete macrodomains 20–200 nm in size occurred at concentrations equal to or slightly lower than the saturation concentration. The macrodomains of the graft copolymers were microphase separated, and the sizes and shapes of the microdomains were found to largely depend on the graft copolymer structure and composition. As a consequence of microphase separation, poly(ethylene oxide) crystallinity was noted in blends with sufficiently high macrophase contents. Observations of a graft copolymer interphase between the polystyrene matrix and the polyamide-6 domains confirmed that the graft copolymer was present at the blend interfaces in some of the compatibilized blends. © 1996 John Wiley & Sons, Inc. 相似文献
15.
本文用透射电子显微镜(TEM),光学显微镜(OM),小角X射线散射(SAXS)等方法研究了聚甲基丙烯酸β羟乙酯(HEMA)在聚乙烯(PE)膜上辐射接枝物的形态结构.观察了微相结构随接枝条件变化规律.HEMA为支链的接枝共聚物的基本形态是高度分散的HEMA微区(约几百A)存在于PE连续相中的两相体系.随接枝量增加,微区形态发生变化.SAXS结果进一步证实了接枝共聚物相分离的形态结构,并利用Tsvankin-Buchanan公式计算了共聚物的长周期、无定形层厚及一维结晶度. 相似文献
16.
Series of PTT-b-PEO copolymers with different composition of rigid PTT and PEO flexible segments were synthesized from dimethyl terephthalate (DMT), 1,3-propanediol (PDO), poly(ethylene glycol) (PEG, Mn = 1000 g/mol) in a two stage process involving transesterification and polycondensation in the melt. The weight fraction of flexible segments was varied between 20 and 70 wt%. The molecular structure of synthesized copolymers was confirmed by 1H NMR and 13C NMR spectroscopy. The superstructure of these polymers was characterized by DSC, DMTA, WAXS and SAXS measurements. It was observed that domains of three types can exist in PTT-b-PEOT copolymers: semi-crystalline PTT, amorphous PEO rich phase (amorphous PEO/PTT blended phase) and semi-crystalline PEO phase. Semi-crystalline PEO phase was observed only at temperature below 0 °C for sample containing the highest concentration of PEO segment. The phase structure, thermal and mechanical properties are effected by copolymer composition. The copolymers containing 30÷70 wt% of PEO segment posses good thermoplastic elastomers properties with high thermal stability. Hardness and tensile strength rise with increase of PTT content in copolymers. 相似文献
17.
Dilute solution properties of linear (SI)3 six-block copolymers of styrene and isoprene are compared to those of random, two-block, and three-block copolymers of the same system. All the copolymers were prepared with sec-butyllithium in benzene. The microstructure of the polyisoprene blocks is close to that of homopolyisoprene prepared under the same conditions. In contrast, the random copolymer shows a larger amount of trans-1,4 isoprene units. The intrinsic viscosities of the copolymers in methylisobutyl ketone, a poor solvent for both polystyrene and polyisoprene, and in toluene, a good solvent for both homopolymers, are examined on the basis of the Fox–Flory relation for homopolymers. All the copolymers behave similarly in each solvent. In methylisobutyl ketone, the viscosity results indicate a random coil conformation with a small expansion owing to the extra repulsive interactions between the dissimilar units. In all cases, the heterocontact repulsive interactions are small and can be characterized by an interaction parameter χab close to 0.025. In toluene, the perturbation caused by the heterocontacts becomes negligible and the expansion factor αη can be predicted from a weighted average of those of the parent homopolymers of the same molecular weight as the copolymer. 相似文献
18.
A series of block sulfonated poly(arylene ether ketone) (SPAEK) copolymers with different block lengths and ionic contents were synthesized by a two‐stage process. The morphology of these block SPAEK copolymers was investigated by various methods, such as differential scanning calorimetry (DSC), transmission electron microscope (TEM), and small angle X‐ray scattering (SAXS). Dark colored ionic domains of hundreds of nanometers spreading as a cloud‐like belt were observed in TEM images. The sizes of the ionic domains as a function of block copolymer composition were determined from SAXS curves. The results for the evolution of ionic domains revealed that the block copolymers exhibited more clearly phase‐separated microstructure with increasing ionic contents and hydrophobic sequence lengths. Proton conductivity is closely related to the microstructure, especially the presence of large interconnected ionic domains or ionic channels. Block SPAEK membranes have interconnected ionic clusters to provide continuous hydrophilic channels, resulting in higher proton conductivity. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
19.
The image contrast inversion was investigated in detail when soft polymeric materials were imaged with tapping mode atomic force microscopy (TM-AFM). Solvent cast film of polystyrene-block-poly(ethylene/butylene)block-polystyrene (SEBS) triblock copolymers was used as a model system in this study, which showed phase separation domains with a size of several tens of nanometers. AFM contrast reversal process, through positive image, to an intermediary and till negative image, could be clearly seen in height images of the soft block copolymer using different tapping force. The higher tapping force would lead to not only contrast inversion, but also the different size of the microdomains and different roughness of the images. Moreover, contrast inversion was explained on the basis of attractive and repulsive contributions to the tip-sample interaction and indentation of the soft domains. 相似文献
20.
Byoung‐Ki Cho Seung‐Hyun Kim Eunji Lee 《Journal of polymer science. Part A, Polymer chemistry》2010,48(11):2372-2376
We prepared two block copolymers 1 and 2 consisting of a third‐generation dendron with poly(ethylene oxide) (PEO) peripheries and a linear polystyrene (PS) coil. The PS molecular weights were 2000 g/mol and 8000 g/mol for 1 and 2 , respectively. The differential scanning calorimetry (DSC) data indicated that neither of the block copolymers showed glass transition, implying that there was no microphase separation between the PEO and PS blocks. However, upon doping the block copolymers with lithium triflate (lithium concentration per ethylene oxide unit = 0.2), two distinct glass transitions were seen, corresponding to the salt‐doped PEO and PS blocks, respectively. The morphological analysis using small angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM) demonstrated that a hexagonal columnar morphology was induced in salt‐doped sample 1‐Li+ , whereas the other sample ( 2‐Li+ ) with a longer PS coil revealed a lamellar structure. In particular, in the SAXS data of 2‐Li+ , an abrupt reduction in the lamellar thickness was observed near the PS glass transition temperature (Tg), in contrast to the SAXS data for 1‐Li+ . This reduction implies that there is a lateral expansion of the molecular section in the lamellar structure, which can be interpreted by the conformational energy stabilization of the long PS coil above Tg. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2372–2376, 2010 相似文献