Characterization of static and dynamic properties of a low-density polyethylene. Evidence for translocation of fluorescent probes upon stretching and determination of relaxation processes at the mesoscopic level

被引:40
作者
Talhavini, M
Atvars, TDZ
Cui, C
Weiss, RG
机构
[1] UNIV ESTADUAL CAMPINAS,INST QUIM,BR-13084100 CAMPINAS,SP,BRAZIL
[2] GEORGETOWN UNIV,DEPT CHEM,WASHINGTON,DC 20057
基金
巴西圣保罗研究基金会; 美国国家科学基金会;
关键词
fluorescence; low-density polyethylene; relaxation;
D O I
10.1016/0032-3861(96)00273-X
中图分类号
O63 [高分子化学(高聚物)];
学科分类号
070305 ; 080501 ; 081704 ;
摘要
Fluorescence from anthracene guest molecules (AN) has been used to study secondary alpha, beta and gamma relaxation processes in unstretched and stretched low density polyethylene (LDPE) in the temperature range 15-400 K. The LDPE was characterized by several different techniques. It contains about 4 vinylidene, vinylene and vinyl type C=C bonds and about 320 CH3 groups per 10 000 CH2 units. The unstretched polymer is 31% crystalline and has a melting point, T-m, of 109 degrees C. The 5x stretched polymer is 51% crystalline and T-m = 110 degrees C. Although the degree of crystallinity of the films suffers a large change upon macroscopic stretching, the melting temperature (determined by d.s.c. and fluorescence spectroscopy) and the relaxation temperatures do not. However, plots of total fluorescence intensity or fluorescence intensity ratios at different wavelengths vs temperature indicate that dynamic processes involved with the excited singlet states of anthracene are dependent upon polymer stretching. These results, in combination with others obtained previously, suggest that stretching reduces the average amount of free volume at guest sites and induces a translocation of anthracene molecules toward sites at the crystalline-amorphous interfaces. Copyright (C) 1996 Elsevier Science Ltd.
引用
收藏
页码:4365 / 4374
页数:10
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