MEAN-SQUARE RADIUS OF GYRATION AND DIPOLE MOMENT OF POLY(METHYLPHENYLSILOXANE) CHAINS

The mean-square radius of gyration ,the mean-square dipole moment ,the mean-square end-to-end distance and their temperature coefficients of unsymmetrical disubstituted poly(methylphenylsiloxane) (PMPS) chains, as a function of stereochemical structure,confomational energies and length of polymers,were studied by using an improved configurational-confomational statistical method based on the rotational-isomeric-state theory.It is found that the increase in isotacticity of PMPS chains caus...     

STUDY ON MEAN-SQUARE RADIUS OF GYRATION FOR POLYALKYLENEOXIDES

Taking account of the effect of heteroatoms in backbone, this article dealt with themean-square radii of gyration of polyalkyleneoxides by the approach of matrix algebrain accordance with the rotational isomeric state model. Numerical calculation with theparameters available in the literatures indicated that the dependence of on themolecular weight can be expressed by the general formula: = aM~b     

INVESTIGATION OF THE USE OF POLY(3,4-EPOXY-1-BUTENE) IN FREE RADICAL PHOTOPOLYMERIZATIONS

ABSTRACT

The use of poly(3,4-epoxy-1-butene) (polyEPB) in photoinduced free radical polymerizations has been investigated. It was observed that the inclusion of polyEPB into these photopolymerizations has several beneficial effects. In combination with aromatic ketones, polyEPB functions as a hydrogen donor to form a highly effective photoinitiator for the polymerization of acrylate monomers. At the same time, polyEPB undergoes facile autoxidation that serves to mitigate inhibition effects due to oxygen during free radical photopolymerizations. PolyEPB is an effective chain transfer agent that tends to increase both the rate and conversion in photoinduced crosslinking polymerizations in which multifunctional monomers are employed. Lastly, polyEPB is a interesting matrix-modifying agent that becomes incorporated into the resin matrix during photopolymerization due to photoinduced grafting reactions.     

CONFORMATIONAL CHARACTERISTICS OF POLY(ACRYLIC ACID) AND POLY(METHACRYLIC ACID)

A full-relaxation optimization of molecule and the Dreiding force field are employed toobtain the geometry parameters and the conformational energy surfaces of meso or racemicdyad of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA). Three differentcarbonyl-bond orientations of side-groups resulted in the differences in depth of potentialwells in their energetic contours for a meso or a racemic dyad. These discrepancies areinterpreted as a result of various fine structures corresponding to grid search conformationsas well as thereby different interactions. The analysis on the most stable conformationsof PMAA confirmed that the ester groups are nearly perpendicular to the plane definedby the two adjacent skeletal bonds but may possibly change their relative orientations tomeet the requirement of lower energy during the conformational state transition. For eachpolyme, two global energy maps of a meso and a racemic dyad were finally constructedfrom the superposition of energy data for the three kinds of side-group orientations by theBoltzmann factors. From an ensemble average, the proposed scheme with three rotationalisomeric states (RIS) allowed us to access the experimentally unperturbed dimensions ofPAA chain via the configurational statistical mechanics. Although the calculation wasbased on the short-range, local interactions, it was interested to note that the experimentalcharacteristic ratios just fell within the range calculated for atactic chains.     

STUDY ON LIQUID CRYSTALLINITY OF POLY(N-VINYLCARBAZOLE)

The liquid crystallinity of poly(N-vinylcarbazole) was studied by using powder X-ray diffraction, polarized opticalmicroscopy, and differential scanning calorimetry. The results show that the lower molecular weight fractions of this polymerdo not form a liquid crystalline phase, while the samples of sufficiently high molecular weight do form a mesophase attemperatures above the glass transition. The lowest value of the degree of polymerization for PVK to form a stable liquidcrystalline phase was found to be in the range of 150 to 200, significantly higher than the value of 50 for most conventionalside chain liquid crystaline polymers.     

PHOTOINITIATED CATIONIC POLYMERIZATION OF EPOXY MONOMERS IN THE PRESENCE OF POLY(3,4-EPOXY-1-BUTENE)

ABSTRACT

Hydroxyl-terminated poly(3,4-epoxy-1-butene) (polyEPB) is an interesting and highly useful agent for the acceleration of the photoinitiated cationic ring-opening polymerization of epoxide monomers. Kinetic investigations using real-time infrared spectroscopy have shown that the observed acceleration of the polymerization is due to two independent mechanisms. Crosslinking polymerization of epoxide monomers is accelerated due to an activated monomer mechanism that results in facile chain transfer due to interaction of the terminal hydroxyl groups of polyEPB with the growing oxonium ion chain ends. A second mechanism involving participation of polyEPB in a free radical chain induced decomposition of the onium salt photoinitiator is mainly responsible for the observed acceleration in the rate of polymerization. A large number of polymer-bound carbocationic species are generated by this mechanism that are capable of initiating polymerization of the epoxide monomer.     

聚卤乙烯单体性质及构型对链柔性和极性的影响

基于旋转异构态模型和生成矩阵统计方法,推导了极性取代基高分子链均方回转半径和均方偶极矩改进的计算公式,应用于研究聚卤乙烯链构象和构型依赖的性质,包括均方回转半径和偶极矩特征比与构象能、链规整程度和温度的关系.发现构型规整的聚卤乙烯链特征比、温度系数和构象能依赖性质均呈现较大的差异,尤其是间同和全同构型链.如聚卤乙烯间同链偶极矩特征比随主要相互作用Eη变化比例在-0.62～0.05(J/mol)-1之间.相反,构型不规整的聚卤乙烯链的无扰尺寸则比较接近.聚氟乙烯、聚氯乙烯和聚溴乙烯无规链均方偶极矩特征比分别为0.80、0.69和0.59,均方偶极矩温度系数为-0.07×10-3～-0.53×10-3 K-1,与实验结果符合.研究结果表明聚卤乙烯单体性质和构型对其链柔性和链极性的影响是显著的.     

SYNTHESIS AND CRYSTALLIZATION BEHAVIOR OF POLY(ETHER ETHER KETONE ETHER KETONE)(PEEKEK)*

In this paper, the synthesis and crystallization behavior of poly(ether ether ketone ether ketone) (PEEKEK) arereported. PEEKEK was prepared from 4,4'-bis(p-fluorobenzoyl) diphenyl ether (4,4'-FBDE) and hydroquinone along thenucleophilic substitution route. The thermal properties were investigated by using DSC and TGA. The crystallizationbehavior of PEEKEK under several conditions, i.e., crystallization from the molten state (melt crystallization), crystallizationfrom a quenched sample (cold crystallization) and crystallization induced by exposing glassy sample to methylene chloride(solvent-induced crystallization) has also been investigated. The results show that crystallization of PEEKEK could beinduced by the above methods, and no polymorphism was found. The diflierences in the crystallization of PEEKEK inducedby the above methods are seen in their degree of crystallinity.     

茂金属催化聚合的聚1-丁烯的结构表征

以 η5 五甲基茂基三苄氧基钛 (Cp Ti(OBz) 3 和改性甲基铝氧烷 (mMAO)为催化剂 ,合成立体嵌段聚 1 丁烯 ,分子量高 ,分子量分布窄 ( Mw/ Mn=1 1～ 1 2 ) .聚合产物经沸乙醚、沸庚烷连续抽提分离 ,聚合物在两种溶剂中都能部分溶解 .各级份经13C NMR ,WAXD ,DSC和GPC等手段分析 ,结果表明乙醚可溶级份是无规聚 1 丁烯 ,庚烷可溶级份是立体嵌段聚 1 丁烯 ,庚烷不溶级份是等规聚 1 丁烯 .聚合温度较低 (0℃和30℃ )时 ,聚合物有结晶性 ,结晶度达 30 %以上 ,DSC分析有两个吸热峰 ;聚合温度较高 (4 0℃ )时 ,聚合物无结晶尖锐X射线衍射峰 ,也无熔融吸热峰 .     

EFFECT OF SOLVENT COMPOSITION ON THE SULFONATION DEGREE OF POLY(PHENYLENE OXIDE) (PPO)

This paper investigates the possibility of attaining sulphonated poly(phenylene oxide) (SPPO) with a relativelyhigher sulfonation degree. To achieve this aim, the approach we adopt is to improve the solubility of the final product in themixed solvent so that the sulfonation may take place between the bulk solutions and PPO powders even at higher sulfonationdegree. It is shown that the addition of a proper amount of dimethyl formide (DMF) to the conventional PPO-chloroformsystem can actually enhance the sulfonation effect. The solvent composition is then correlated with the sulfonation degreebased on the solubility parameters. It is interesting to find that solubility parameters between the mixed solvent and theprecipitated products keep an approximately unchanged value at about 4.9, which is just equal to that when pure chloroformis used, though the solubility parameters of both solvents increase with the content of DMF in solution. This may be the mainreason why the addition of DMF can reduce the precipitation and improve the ion exchange capacity (IEC) of SPPOpolymer.     

COMPUTER SIMULATIONS ON UNPERTURBED CONFIGURATIONAL DIMENSIONS OF POLY (METHYL ACRYLATE)

A full-relaxation optimization of molecule and the popular MM2 force field are em-ployed to obtain the geometry parameters and the conformational energy surface of a mesoor a racemic dyad of poly(methyl acrylate) (PMA) with a specified carbonyl-bond orien-tation in side-groups. It is found that the conformational energy maps calculated hereconsiderably differ from those calculated with the rigid molecular model as reported in theearlier studies. The g~- state cannot be omitted in the obtained contour maps. Two impor-tant conformers tg~- and g~(-t) with energy minima were newly detected for a racemic dyad.The analysis on the conformations with energy minima confirmed that the ester groupsare not always perpendicular to the plane defined by the two adjacent skeletal bonds andmay change their relative orientations to meet the requirement of lower energies duringthe conformational state transition. Instead of the early way of adjusting the interactionenergy parameters to fit the experimental data, we attempt to predict unperturbed chaindimensions via the reliable force field and the configurational statistical mechanics. Theproposed scheme with three rotational states identified from the contour maps allowed usto satisfactorily reproduce the experimental dimensions of random PMA chains.     

CONFIGURATION-DEPENDENT PROPERTIES OF POLY(DIMETHYLSILOXANE) CHAIN*

The intermolecular rotational potential energies for poly(dimethylsiloxane) (PDMS) chains aredirectly obtained from a priori probability P_(αβ). Here the differing statistical weight matrices for the Si-Oand O-Si bonds are considered in calculating the configuration partition function. In the Bahar's model, asthe same statistical weight matrices for the Si -O and O- Si bonds are adopted, there exists a large deviationof αpriori probability P_(αβ) between the theory and the molecular dynamics (MD) simulation. Our model givessatisfactory agreement with experiment on the mean-square unperturbed end-to-end distance, the mean-square dipole moment and its temperature dependence, and the molar cyclization equilibrium constants fordimethylsiloxane oligomers. This new rotational isomeric state approach can be widely applied to otherchains, such as -CH_2-C[(CH_2)_mH]_2- and -O-Si[(CH_2)_mH]_2 for arbitrary m.     

聚四氟乙烯和聚二甲基硅烷的链尺寸和偶极矩

基于改进的旋转异构态方法,推导了对称双取代基高分子链的均方回转半径和均方偶极矩公式,用于研究聚四氟乙烯(PTFE)、聚二甲基硅烷(PDMS)和聚乙烯(PE)链构象依赖的性质.计算得到长链聚四氟乙烯PTFE4(四态模型)和PDMS的构型参数值分别为0.44·mol0.5·g-0.5和0.43·mol0.5·g-0.5,PDMS链的相应温度系数值-7.32×10-3K-1,它与PTFE和PE的值(约-1.00×10-3K-1)相差较大.得到长链PTFE和PDMS的均方电偶极矩特征比结果都很小,如PDMS链的特征比为0.27,说明虽然PTFE和PDMS的侧基键C—F和Si—CH3都有强极性,但其聚合物却是非极性的电介质,具有较好的电绝缘性能,可见高分子链的构象和结构也对聚合物极性和电学性质有很大的影响.得到短链PTFE和PDMS(重复单元x10)均方偶极矩表现出明显的端点效应,特征比随x的改变而呈现明显的波动,这与Flory等的计算结果一致.     

聚(L-丙交酯)/聚(DL-丙交酯)的结晶性能及相溶性

用共溶液沉淀法制备了聚 (L 丙交酯 ) 聚 (DL 丙交酯 )共混物 (PLLA PDLLA) ,然后用成纤模压法压制成3 2mm的棒材 .用差示扫描量热法研究了共混物的结晶性能和相溶性 .结果表明 ,PLLA组分在共溶液沉淀过程中可生成结晶 ,共混物中PDLLA含量直到 30 %时 ,PLLA组分的结晶熔融温度和结晶度与纯PLLA相同 ,但PDLLA含量为 5 0 %时 ,PLLA组分的结晶熔融温度和结晶度明显下降 .由于加工成型条件的不一致性 ,共混物棒材中的PLLA组分的结晶熔融温度和结晶度呈较大的分散性 .共混物从熔体降温 ,在其后的升温DSC扫描中出现分别相应于PDLLA和PLLA的玻璃化转变 ,表明PDLLA与未结晶的PLLA形成的非晶相是不相溶的     

SYNTHESIS AND CHARACTERIZATION OF POLY(ARYL ETHER KETONE)CONTAINING BIPHENYLPHTHALAZINONE MOIETY*

A new poly(aryl ether ketone) containing biphenylphthalazinone moiety was prepared by thereaction of 4-(4-hydroxybiphenyl) phthalazine-1-one with 4, 4'-difluorobenzophenone. The monomer and thepolymer were characterized by FT-IR and ~1H-NMR. Some properties of this polymer were described.     

SYNTHESIS AND OPTICAL PROPERTIES OF POLY (THIENYLACETYLENES)*

3 -Ethynyl-4-(trimethylsilyl)thiophene (1a) and 3 -ethynyl-4-bromothiophene (1 b ) selectivelyundergo acetylene polymerizations in the presence of the MoCl_5- and WCl_6-Ph_3SiH catalysts to give soluble,high-molecular-weight poly(thienylacetylenes) (2) (M_w up to 602000) in high yields (up to 100%). Lighttransmission spectra of THF solutions of 2 continuously red-shift with increasing concentration. Theconcentratochromism shows a logarithmic concentration dependence; that is, the optical transitions of 2 arepredictably tunable by simply changing their concentrations.     

STRUCTURE AND PROPERTIES OF POLY (N-VINYLCARBAZOLE) OBTAINED VIA ASYMMETRICALLY STEREOSELECTIVE POLYMERIZATION

The structure and properties of poly(N-vinylcarbazole) (PVCZ) obtainedvia asymmetrically stereoselective polymerization have been studied by using ~1HNMRspectra, UV spectra, DSC analysis and GPC. The steric microstructure i.e. the contentof isotactic sequences was found to be increased by using AIBN to (-)Sp~+(+)CSA~- asthe initiators or catalysts and the mole extinction coefficient to be decreased. Bimodalmolecular weight distribution (MWD)s of the obtained PVCZs were caused by two propa-gating species of the free ions and the ion-pairs associated with the organic salts duringpolymerization.     

CLOUD POINT CURVES OF POLY(ETHYLENE GLYCOL)/POLY(PROPYLENE GLYCOL) MIXTURES AND THEIR THERMODYNAMIC EXPLANATION

In the study of poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) mixtures not only a bimodal shape but also a reverse trend of the dependence on molecular weight of the cloud point curves were observed.This trend indicates that the miscibility of the studied mixtures decreases as the molecular weight of one component decreases. The excess volumes of the mixtures show that the interaction parameter between two components decreases at first and increases after passing a minimum as the concentration of one component increases. This supports the explanation of Koningsveld on the bimodal shape of cloud point curves. Based on a binary interaction model a formula was derived revealing that the interaction between PPG and the end group of PEG and the hydrogen bonding interaction between ether and hydroxy end group inner or inter PEG molecules are not favorable for mixing. The latter interaction is an "attractive" force in PEG molecules. The two interactions are responsible for the observed abnormal dependence.     

SURFACE OF GELATIN MODIFIED POLY(L-LACTIC ACID)FILM

In this paper, the surface structure of poly(L-lactic acid) (PLLA) film modified with gelatin was investigated. ThePLLA film specimens were treated directly with aqueous alkali solution to provide their surfaces with carboxyl groups, sothat these functional groups could become the reactive sites for gelatin immobilization. The functional groups of the PLLAfilms were identified by ATR-FTIR spectra and XPS spectra, the changes in surface morphology were observed by usingenvironmental scanning electron microscopy (ESEM), and the hydrophilicity of modified PLLA films was examined bywater contact angle measurement. Experimental results showed that the gelatin was immobilized with water-solublecarbodiimide (EDC) onto the PLLA film's surfaces, and the gelatin content on the polymer surface was related to carboxylicgroup formed in the controlled hydrolysis process. Rough surfaces caused by hydrolysis will predominantly favor the adhesion and growth of cell; and the hydrophilicity of these surfaces after the modification procedure is enhanced.     

INFLUENCE OF TRACES OF WATER ON THE SYNTHESIS AND ELECTROLUMINESCENCE PROPERTIES OF POLY(2-METHOXY, 5- (2'''' -ETHYLHEXYL OXY)- 1, 4-PHENYLENE VINYLENE)

It was found that traces of water in the reaction medium would result in a great increase of gel and a decrease ofmolecular weight of the poly(2-methoxy, 5-(2'-ethylhexyloxy)-1, 4-phenylene vinylene) during the polymerization, whichultimately led to inferior film qualities and device properties. The device (ITO/PEDOT/MEH-PPV/Ba/Al) with MEH-PPVprepared under dry conditions has an external quantum efficiency of above 2.0%.