Synthesis of styrene–acrylonitrile random copolymers (SAN) and polyarylate block copolymers and the control of their mechanical properties by morphology generation

The idea of repulsion in random copolymers was applied to the miscibility modification between polystyrene (PS) and polyarylate (PAr) segments of PS–PAr block copolymer (PAr–PS–PAr). Acrylonitrile (AN), which has a large positive interaction parameter against styrene, was used as a miscibility modifier toward PAr segments. AN was introduced into the carboxyl terminated telechelic‐PS at AN wt % ranging from 12 to 37 wt %. Based on these telechelic acrylonitrile–styrene random copolymers (SAN_x's where x represents AN wt %), SAN_x and PAr block copolymers (PAr–SAN_x–PAr's) were synthesized. The miscibility of SAN_x and PAr segments was estimated from the results of DSC with Fox's equation and spin–spin relaxation time measured by pulsed NMR. These results evidenced that the miscibility between PS and PAr segments can be modified by introducing AN into PS segments. The estimated volume fraction of the interfacial layer between SAN_x and PAr segments was increased as x was increased toward 24 wt %, around which the predicted miscibility reaches a maximum. Above that AN wt %, it began to decrease. The flexural strength increased as the miscibility between SAN_x and PAr segments increased. In particular, when x was between 20 and 30 wt %, PAr–SAN_x–PAr exhibited three times larger flexural strength than PAr–PS–PAr. The fracture behavior changed from brittle to ductile, even though the telechelic SAN_x by themselves exhibited almost the same fracture strength as the telechelic PS. The results of dynamic mechanical measurements and the percolation model suggested that around these AN wt % the continuum matrices in PAr–SAN_x–PAr changed from SAN_x phase to a cocontinuous phase of SAN_x and PAr. From these results, PAr–SAN_x–PAr was explained to perform such a high flexural strength by this phase change in the continuum matrices. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 127–137, 2000     

The structure and physical properties of in situ composites based on semiflexible thermotropic liquid crystalline copolyesteramide and poly(butylene terephthalate)

Liquid crystalline polymer–poly(butylene terephthalate) (LCP/PBT) blends were prepared by melt mixing. The LCP employed was a thermotropic copolyesteramide based on 30 mol % of p‐amino benzoic acid (ABA) and 70 mol % of poly(ethylene terephthalate) (PET). The thermal, dynamic mechanical and rheological properties, morphology, and crystal structure of LCP/PBT blends were studied. The results showed that the semiflexible ABA30/PET LCP is miscible in the melt state with PBT, and they are partial miscible in the solid state. Differential scanning calorimetric measurements showed that the introduction of the semiflexible LCP into LCP/PBT blends retards the crystallization rate of PBT. However, the LCP dispersed phase acted as the sites for the nucleation of spherulites and enhance the degree of crystallinity of PBT. Hot‐stage optical microscopy examination revealed that the LCP microfibers with random orientation are dispersed in the PBT matrix of compression molded LCP/PBT blends. Under the application of a shearing force, the LCP domains in the PBT matrix tended to deform into microfibers, and to orient themselves along the flow direction. The formation of microfibers resulted in an increase of the storage modulus. The torque measurements indicated that the melting viscosity of the LCP/PBT blends is much lower than that of the pure PBT. Finally, the wide‐angle X‐ray diffraction patterns indicated that PBT shows no structural change with the incorporation of LCP, but the apparent crystal sizes of several diffraction planes change significantly. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 403–414, 2000     

Miscibility of Polyoxymethylene Blends as Revealed by High-resolution Solid-state 13C-NMR Spectroscopy

The miscibility of polyvinylphenol (PVPh) or terpenephenol (TPh) with polyoxymethylene (POM) was examined by high-resolution solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy. It was found that the driving force for the mixing of POM and PVPh is the hydrogen-bonding interaction between the phenolic OH group of PVPh and the ether oxygen of POM, and that the mixing is preferentially induced in the noncrystalline phase. ¹H relaxation time experiments indicated that POM/PVPh blends were homogeneous on a scale of 20–30 nm but heterogeneous on a scale of 2–3 nm. On the other hand, Fourier transform infrared and cross-polarization/magic-angle-spinning ¹³C-NMR (nuclear magnetic resonance) spectra revealed that POM and TPh are also mixed in the noncrystalline phase through the intermolecular hydrogen-bonding interaction, while some fraction of POM is still crystallizable. Moreover, the domain size of the micro-phase separation was estimated to be about 1 nm by the direct ¹H spin-diffusion measurements, suggesting almost homogeneous mixing on a molecular level in the noncrystalline phase. © 1997 John Wiley & Sons, Ltd.     

Miscibility and crystallization behavior of solution-blended PEEK/PI blends

Miscibility and crystallization behavior of solution-blended poly(ether ether ketone)/polyimide (PEEK/PI) blends were investigated by using DSC, optical microscopy and SAXS methods. Two kinds of PIs, YS-30 and PEI-E, which consist of the same diamine but different dianhydrides, were used in this work. The experimental results show that blends of PEEK/YS-30 are miscible over the entire composition range, as all the blends of different compositions exhibit a single glass transition temperature. The crystallization of PEEK was hindered by YS-30 in PEEK/YS-30 blends, of which the dominant morphology is interlamellar. On the other hand, blends of PEEK/PEI-E are immiscible, and the effect of PEI-E on the crystallization behavior of PEEK is weak. The crystallinity of PEEK in the isothermally crystallized PEEK/YS-30 blend specimens decreases with the increase in PI content. But the crystallinity of PEEK in the annealed samples almost keeps unchanged and reaches its maximum value, which is more than 50%. The spherulitic texture of the blends depends on both the blend composition and the molecular structure of the PIs used. The more PI added, the more imperfect the crystalline structure of PEEK. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2267–2274, 1998     

Thermal characterization and solid‐state 13C‐NMR investigation of blends of poly(N‐phenyl‐2‐hydroxytrimethylene amine) and poly(N‐vinyl pyrrolidone)

The miscibility and thermal properties of poly(N‐phenyl‐2‐hydroxytrimethylene amine)/poly(N‐vinyl pyrrolidone) (PHA/PVP) blends were examined by using differential scanning calorimetry (DSC), high‐resolution solid‐state nuclear magnetic resonance (NMR) techniques, and thermogravimetric analysis (TGA). It was found that PHA is miscible with PVP, as shown by the existence of a single composition‐dependent glass transition temperature (T_g) in the whole composition range. The DSC results, together with the ¹³C crosspolarization (CP)/magic angle spinning (MAS)/high‐power dipolar decoupling (DD) spectra of the blends, revealed that there exist rather strong intermolecular interactions between PHA and PVP. The increase in hydrogen bonding and in T_g of the blends was found to broaden the line width of CH—OH carbon resonance of PHA. The measurement of the relaxation time showed that the PHA/PVP blends are homogeneous at least on the scale of 1–2 nm. The proton spin‐lattice relaxation in both the laboratory frame and the rotating frame were studied as a function of the blend composition, and it was found that blending did not appreciably affect the spectral densities of motion (sub‐T_g relaxation) in the mid‐MHz and mid‐KHz frequency ranges. Thermogravimetric analysis showed that PHA has rather good thermal stability, and the thermal stability of the blend can be further improved with increasing PVP content. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 237–245, 1999     

Phase behavior and some calorimetric and physical properties of diurethanes from perfluoropolyether macromonomers

Density and calorimetric measurements have been carried out on copolymeric perfluoropolyethers of molecular weight ranging between 500 and 4700, terminated at both chain ends either with  CH₂OH or ethylurethane groups. Samples of the second series are models for perfluoropolyethers based polyurethanes. Density measurements point out that the terminal alcoholic group brings about a negative excess volume, which increases with decreasing the molecular weight; a lower excess volume is found for urethane‐terminated molecules. Calorimetric traces, T_g, and Δc_p at T_g show that alcoholic‐terminated molecules are amorphous and one phase systems, while urethane‐terminated compounds are crystalline; phase separation is observed for this last series when the molecular weight of the fluorinated segment is larger than 1000. The trend of T_g with molecular weight is discussed for one‐ and two‐phase systems in the light of current theories for the glass transition. The decrease of the melting point with increasing the molecular weight for the urethane series can be described by the Flory equation for random copolymers. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1609–1622, 1999     

Al-Zn-Cu三元系Al-Zn侧相平衡成分的测定

采用扩散偶电子探针微区分析技术,对Al Zn Cu三元系相图的低Cu区三个固溶体相的相平衡关系及相平衡成分进行了研究·结果发现,在320℃时Cu的加入使得α1/α2,α2/β相平衡时的α1和α2中的Zn含量都降低·在260℃时,添加少量的Cu使得α/β平衡时α中的Zn含量增加·Cu在α1/α2,α2/β和α/β三种相平衡时的分配都不对称,即Cu在后者中的含量远大于前者·这意味着在320℃时Cu的加入使得α1/α1+α2相边界向富Al角趋近;在260℃时Cu的加入使得α/α+β相边界向Zn含量增加的方向偏移·     

Transmission electron microscopy study of phase morphology in polypropylene/ethylene-octene copolymer blends

Blends of polypropylene (PP) and ethylene-octene copolymers (EOC) were investigated by transmission electron microscopy (TEM) and by differential scanning calorimetry (DSC). The EOC contained 28, 37, 40 or 52 wt% of octene. Only the 50/50 PP/EOC ratio was used for all blends. None of the blends was fully miscible, there was always two-phase morphology. TEM observation followed by image analysis by ImageJ software revealed that the largest particles were in blend containing EOC-28 and the smallest were in blend with EOC-52. The coarsening rate at 200 °C was evaluated by TEM. The glass transition temperature (T_g) shift indicated partial miscibility. Partial miscibility was then confirmed by direct observation of bright PP lamellae in EOC dark phase.     

EA/POSS纳米复合材料的相容性及热稳定性

采用紫外光固化技术,通过机械共混的方法制备了甲基-多面体齐聚倍半硅氧烷(甲基-POSS)质量分数分别为1%,5%,10%,15%的环氧丙烯酸酯(EA)/POSS纳米复合材料.通过X射线衍射、扫描电子显微镜、EDS能谱分析及热重分析对环氧丙烯酸酯(EA)/POSS纳米复合材料进行研究.结果表明,在甲基-POSS质量分数较高时,EA/POSS纳米复合材料中存在甲基-POSS晶体,说明杂化材料中存在相分离.甲基-POSS在聚合物中以分子或团聚体的形式存在,并且随着POSS质量分数的增加,团聚体尺寸及数量都逐渐增多.甲基-POSS单体提高了复合材料的热稳定性,并且POSS的加入并没有影响聚合物的热降解机理.     

共聚物混溶性热力学-分子内排斥作用与附加共聚焓

基于聚合物分子间物理相互作用和统计平均场理论,引入附加共聚焓定义,使聚合物分子间的作用得到量化,同时推导出二元共混体系相互作用参数和三元共混体系混合焓关系式.利用所导出的公式解释一些常见聚合物共混体系和增溶体系.导出的关系式很好地解释了聚合物的热力学混溶性,但不能解释聚合物共混增溶作用.