BF_3,络合的丙烯酸乙酯与丙烯的共聚机理

BF_3络合的丙烯酸乙酯(EA)与丙烯(P)在25℃进行自由基共聚。聚合速率和引发剂浓度的平方根成直线关系。链转移剂CCl_4可显著影响共聚物的[η];溶剂的介电常数越小,共聚反应速率越大;两种单体浓度相等时共聚反应速率最大。~1H-NMR和 _13C-NMR表明,当[EA·BF_3]/[EA·BF_3]+[P]>O.5时所得共聚物为富于EA的无规共聚物。实验数据表明,共聚反应按三元络合物与二元络合物的无规共聚机理进行,当[EA·BF_3]/[EA·BF_3]+[P]<0.5时,得到交替共聚物,共聚反应按三元络合物均聚机理进行。UV光谱测得了戊烯-1(丙烯的同系物)与EA·BF_3三元络合物的存在,这对三元络合物的均聚机理是有力的证据。     

Retention and selectivity of aromatic hydrocarbons with mono-substituted polar groups in ternary RP-HPLC systems

Summary The variation in selectivity for aromatic hydrocarbons with mono-substituted polar groups is investigated in ternary mobile-phase systems on C₁₈ stationary phases. The dependence of log k′ on the proportions of two modifiers was determined for the solutes within the concentration range of ternary systems obtained by mixing two binary eluents: methanol + water and tetrahydrofuran + water or acetonitrile + water and tetrahydrofuran + water. The nature of the relationships is explained in terms of molecular shape, molecular interactions between solute and extracted modifier and the ordering of solvated ligands on the stationary phase.     

Additive-free non-fullerene organic solar cells with random copolymers as donors over 9% power conversion efficiency

The PBDB-TBT1:ITIC-based device obtains PCE of 9.09%, and is insensitive to additive and thermal annealing, and forms microstructural morphology.     

A verification by FTIR spectroscopy of the effect of some local chain conformations on the specific molecular interactions of solvents,esters, and polyesters with PVC

The molecular interactions of poly(vinylchloride) (PVC) with some solvents [cyclohexanone (CH), methyl ethyl ketone (MEK) and N-methylpirrolidone (MP)], esters [dioctylphthalate (DOP) and butyl stearate (BuSt)], and polyesters [poly(ethylene adipate) (PEA) and poly(ε-caprolactone) (PCL)] have been investigated by FTIR spectroscopy. In all cases the band of the carbonyl group is found to shift to lower frequencies, but significant differences between the solvent and the esters, whether polymeric or not, are evidenced. For PVC-solvent systems, the shift proves to increase linearly as PVC/solvent ratio increases, what suggests that only a definite number of polymer sites is involved. From the slopes of the straight lines this effect of composition is shown to increase in the order MP < MEK < CH, i.e., as the basicity of the solvent decreases. In contrast, for the PVC-esters or polyester blends, a nonlinear behavior consisting of two distinct interaction processes, is obtained. The increase of shift as PVC/ester ratio increases is faster in the first process for all PVC-ester systems and it is particularly enhanced for BuSt and, to a lesser extent, for DOP. Instead, during the second process, that increase is of little significance for BuSt relative to DOP and PCL. These results account for the saturation of the polymer structures that are capable of interacting, at different rates depending on the type of ester. Besides, the whole number of those structures appears to be lower than in the case of solvents. The results are discussed on the ground of, on one side, the mechanism of nucleophilic substitution on PVC, in the same solutions and blends, which, as found previously, is of a stereospecific nature, and, on the other, the electron-donor-acceptor concept (EDA) and the hard-soft-acid-base concept (HSAB) as applied to both the interacting agents (solvents and esters) and the isotactic GTGT and GTTG^? triad conformations as well as the heterotactic GTTT. In the light of the resulting conclusions it is suggested that: (i) the linear behavior shown by the solvents obeys the solvent ability to ensure a dynamic equilibrium between the two possible conformations of - mmr - sequence, i.e., GTGTTT and GTTG^?TT, through the preferential interaction with the little likely GTTG^? conformation, the content of which happens so to be constant as long as there are - mmr - sequences in solution; (ii) the nonlinear behavior of PVC-ester or polyester binary systems reveals a nonequilibrium situation and so the conformational change GTGTTT ? GTTG^?TT, which is highly hindered, will occur occasionally depending on the ester nature. This enables one to attribute the fast and the slow interaction processes to the permanent GTTG^?TT conformations derived from the polymerization and to the same conformations formed as the result of the conformational changes, respectively. Strong support for the above novel finding that PVC … O?C interaction is of a local conformational nature is given by two additional investigations. First, a similar study with a PVC sample prepared at ?50°C, shows that the carbonyl band shifts of CH and PCL are appreciably lower than those of PVC prepared at 70°C. The same holds for the blendof PCL with the latter PVC sample after substitution reaction (0.6%) at ?15°C in CH with sodium benzenethiolate (NaBT). Since the PVC obtained at ?50°C and the 0.6% substituted polymer exhibit a lower content of both permanent GTTG^?TT conformations ad -mmr- sequence, these results agree with expectatins and confirm the above suggestions. Secondly, the changes in the C? Cl stretchign frequencies of PVC with increasing amounts of solvent or ester, as extensively studied, clearly indicate the occurrence of the aforementioned conformational change, and so they are consistent with our proposals as to the actual conformational nature of PVC…O? C interactions. © 1995 John Wiley & Sons, Inc.     

Phase behavior and crystallization analysis in binary crystalline blends of syndiotactic polypropylene and ethylene—Propylene random copolymer

The effects of liquid–liquid (L–L) phase separation on the crystallization behavior of binary syndiotactic polypropylene (sPP) and ethylene–propylene random copolymer (PEP) mixtures are examined by phase‐contrast microscopy (PCM), differential scanning calorimetry (DSC), and cloud point measurements. The PCM experiments reveal that blends of sPP and PEP exhibit a lower critical solution temperature behavior in the melt. The L–L phase diagram, constructed in terms of temperature (T) and composition by cloud point measurements, follows the prediction of the Flory–Huggins theory with the interaction parameter between sPP and PEP [χ(T) = 0.01153 ? 4.5738/T (K)]. When the blends are melted within the two liquid‐phase (α and β) regions, because of the fact that each phase domain reaches the equilibrium concentration ? and ? as well as the phase volume fraction ν^α and ν^β, the crystallinity of each component obeys the equation X_C,I = ν^α X + ν^β X, I = PEP, sPP. Also, the equilibrium melting temperatures of both components remain constants, slightly lower than those of neat polymers. For the sPP/PEP blends crystallized from one homogeneous phase in the melt, we observe that the crystallizability of the major component is not greatly affected upon blending. However, the crystallization behavior of the minority component in the presence of the major component is strongly dependent on the crystallization temperature (T_c). When T_c is high, because the decreasing degree of the minority mobility is much greater than the increasing degree of the formed nuclei, the crystallizability of the minor component is depressed significantly. On the other hand, the promotion of the minority crystallizability in the intermediate regime of T_c is mainly because of the large increase of the heterogeneous nuclei upon blending with a major component. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2995–3005, 2004     

Thermal and structural characterization of poly(ethylene-oxide)/keratin blend films

Blends of poly(ethylene oxide) (PEO) and keratin were prepared with the aim of obtaining bio-compatible materials suitable for film and fibre production. Aqueous keratin solutions, prepared by keratin extraction from wool with urea, m-bisulphite and sodium dodecyl sulphates (SDS), filtration and dialysis, were added with different amounts of PEO and solid films were prepared by casting. The addition of SDS prevents protein aggregation. Morphological, thermal and spectroscopic analysis of the films pointed out that keratin hinders the PEO crystallization process, since a progressive decrease in the size of PEO spherulites is observed and the melting point and the related enthalpy decrease with increasing the keratin content. On the other hand, according to thermal and spectroscopic investigations. PEO seems to interfere with the keratin self-assembling giving the protein a different thermal behaviour.     

丙烯酰胺对Span80-Tween85/Isopar M/丙烯酰胺-H2O拟三元体系相行为的影响

考察了丙烯酰胺对水/IsoparM界面张力的影响以及对水溶液中非离子性乳化剂Tween85的助溶效果,并深入探讨了丙烯酰胺对Span80-Tween85/IsoparM/AM-H2O拟三元体系相行为的影响过程。结果表明,丙烯酰胺能够提高Tween85在水溶液中的溶解度,并可有效降低油水界面张力,进而能够扩大Span80-Tween85/IsoparM/AM-H2O拟三元相图的反相乳液区域面积。     

Miscibility enhancement in blends of polystyrene and polyisoprene modified with electron donor–electron acceptor groups

The use of electron donor–electron acceptor groups to enhance miscibility in polymer blends has been investigated, using the immiscible binary pair polystyrene and polyisoprene as the basic materials. These polymers have been modified by copolymerization with monomers that are either donor or acceptor groups. The copolymers synthesized were poly(styrene-stat-N-itaconimidyl-3,5-dinitrobenzoate), which contains the electron acceptor, and poly[isoprene-stat-N-(2-hydroxyethyl) carbazole methacrylate], which contains the electron donor. Blends were examined using differential scanning calorimetry and dynamic mechanical thermal analysis. The criterion of miscibility was taken to be the presence of only one glass transition temperature in the binary blend, and it was established that at least 20 mol% of the donor–acceptor units had to be incorporated into each chain before a stable one-phase blend was obtained. Miscible blends were observed to undergo a “decomplexation” reaction above the blend T_g, to form partially phase separated blends, with each phase rich in one component and diluted by the second. The value of the blend T_g was above that expected from a weighted average of those of the components, indicating that specific intermolecular interactions, probably charge-transfer complexes, which led to nonbonding crosslinking were present in the blend and stabilized the one-phase system.     

γ-辐射对聚丙烯及聚丙烯/聚乙烯共混物结晶熔融行为的影响

<正> 近年人们对于聚丙烯(PP)辐射效应的研究与日俱增,主要目的在于寻求增强PP辐射稳定性的有效途径。迄今为止文献报道的方法有:添加小分子游动剂(mobilizing addi-tives)、抗氧剂、多官能团单体等,笔者曾研究过不同晶型和含少量聚乙烯(PE)链