溶液成膜的温度对聚对苯二甲酸乙二酯结晶度的影响

<正> 用溶液成膜是制备聚合物薄膜的常用方法之一。但是溶液成膜的条件,如成膜温度,溶液浓度等对半结晶聚合物结晶度的影响研究报道较少。制备聚对苯二甲酸乙二酯(PET)非晶态薄膜通常使用熔融热压其后淬火的方法。由于PET在熔点附近易于降解,在薄膜中产生气泡,因而很难制备较大面积的均一厚度的薄膜,如在拉伸试验中所需     

STUDIES ON THE EXCIMER FLUORESCENCE OF POLYPHENYL GLYCIDYL ETHER AND POLYNAPHTHYL GLYCIDYL ETHER

Polyphenyl glycidyl ether (PPGE) and polynaphthyl glycidyl ether (PNGE) have beensynthesized by cationic polymerization and their structures characterized by carbon 13 NMRand 1R, etc. The fluorescence spectra of PPGE, PNGE and their corresponding monomersPGE, NGE as model compounds have been studied. In dilute solutions at room temperature,only monomer fluorescence of the chromophore is observed. Comparison between the spectraobtained from dilute solutions, concentrated solutions and solid film shows that there is excimeremission when polymer chains in solution or in film are sufficiently close to each ocher.From the concentration dependence of the excimer emission, further evidence is obtained forthe existence of interchain excimer interaction in these polymers.     

用红外谱带分离技术研究单向拉伸聚对苯二甲酸乙二酯薄膜的取向

用谱带分离技术可将聚对苯二甲酸乙二酯红外光谱中的1020cm~(-1)谱带分解为1204.2、1021.5和1017.8cm~(-1)三条谱带。可分别表征该高聚物中的晶区反式构象、非晶区反式构象和左右式构象三种结构。通过对这三条谱带的二向色性的测量,不需其他物理手段配合即可直接比较在不同拉伸条件下的聚对苯二甲酸乙二酯薄膜中上述三种结构的取向行为。     

聚四氟乙烯管的透气性测定

设计了一种管状试样的透气池。用气相色谱法测定了聚四氟乙烯管的透气性。实验表明在所测压力范围内由推压法制成的聚四氟乙烯管中气体的透过是一个扩散过程;聚集态结构的变化可对透气性带来很大的影响。     

FOURIER TRANSFORM INFRARED STUDIES OF POLY (ETHYLENE TEREPHTHALATE) FILM IN THE GLASS TRANSITION REGION

Three specimens from a solution-cast poly (ethylene terephthalate) (PET) film, one being liquid-N_2 quenched from 92℃(Q), one being slowly cooled from 92℃(SC) and one being quenched and sub-T_g annealed at 67℃(AN), have been studied by specimen difference spectra Q-SC and AN-Q and temperature difference spectra T-70 and T_2-T_1 for every 2℃steps on heating to 90℃at 2℃/min. SC and AN showed more gauche conformers than Q. That means that the PET chain has more trans conformers at higher temperatures and some of these are frozen during quenching through T_g. A band at 1340 cm~(-1) has been found to be complex containing overlapping bands reflecting trans in crystalline regions and trans in amorphous regions. The temperature difference spectra on heating through T_g showed that the spectral changes in Q are gradual while a rather abrupt change occurs in AN at 80—82℃for the bands at 1340, 1042 and 1020 cm~(-1). No new conformational structure or new vibrational mode is involved. A kind of locking mechanism is suggested which hinders the molecular vibrational changes in AN below T_g until a sudden release occurs at T_g. These locking sites can be nothing else than sites of tighter local packing of chain segments. Consequently it is believed that inter-chain van der Waals attraction energy plays a dominating role in the volume relaxation and sub-T_g annealing of quenched amorphous polymers.     

INTERMOLECULAR EXCIMER INTERACTION IN POLYMERS

A butadiene-styrene copolymer of low styrene eontent (5% Wt.) has been characterizedby ~1H NMR to have only isolated styrene units on the chain. The fluorescence spectra of thesample in dilute solutions of a good solvent (dichlorethane) at 25--26℃ show monomerfluorescence only. Changes of the fluorescence spectra from a good solvent to poor solvents(dichloroethanemethanol mixture), and form dilute to concentrated solutions up to the solidfilm confirm that excimer formation exists between nonadjacent chromophores in the ehainand between interchain chromophores. Comparison of the spectra obtained from a diluteθ-solution and solid film gives us an estimation of the relative importance of the intrachainexcimer interaction and interchain excimer interaction in the solid sample studied. Theseresults may help us visualize the interpenetration and entanglement of polymer coils duringtransition from a dilute solution to a concentrated one and to a solid polymer.     

芳香聚酰胺纤维的结构鉴定方法研究

用红外光谱方法分析了聚对苯甲酰胺(Ⅰ)和聚对苯二甲酰对苯二胺(Ⅱ)的谱带特征及其与结构的关系,指出了两者的区别,并用二向色性观察了薄膜的取向态,改进了化学分析方法,从(Ⅱ)的水解产物中分离和鉴定了对苯二甲酸和对苯二胺,确定了Kevlar-49纤维的结构属于(Ⅱ),还用差热分析方法比较了T_m和T_d等数据。     

低苯乙烯含量的丁二烯-苯乙烯共聚物的激基缔合物荧光研究

本文报导一种低苯乙烯含量(5％,Wt.)的丁二烯-苯乙烯共聚物,经~1H NMR证明其分子链上不存在相邻苯乙烯单元。荧光光谱结果表明,它在良溶剂(二氯乙烷)的稀溶液状态下只呈现单分子荧光。从良溶剂-θ溶剂(二氯乙烷-甲醇体系)及稀溶液-浓溶液-固体之荧光光谱的变化,证明形成了链内非近邻生色团之间和链间生色团之间的激基缔合物(Excimer)。从固体与θ溶剂的激基缔合物荧光的比较,还可区分链内非近邻和链间苯环形成激基缔合物对荧光强度的贡献。这一结果对阐明高分子链内非近邻和链间激基缔合作用提供了新的证据,并有助于了解高聚物本体中相互穿透、相互缠结的无规线团的形态。