1、null快报null* 1998null07null02 l, 1998null07null31;SE Snull 9nullSE S 5; * *Y “ ? ? s L?CV A? 4V A( C/C* 1, ,. T|ts0 “ 638null nullsnull null0null nullnull null1998 MFig. 3null DSC races of aPS samples (a)M n= 2800, ( b)M n=4900, ( c) M n= 6900, ( d) M n= 9700, ( e) M n= 21600,( f) M n= 267000, ( g) M
2、n= 1550000Initial scans:Rescan:Fig. 2null DSC traces of aPS samplesInitial scans: ( a) Mn= 2800, ( b)M n= 4900,(c)M n= 9700Rescan: ( d) Mn= 9700C/C* .REFERENCES1null Schreiber H P, Ajji A, Li Y, et al. Current Topics in Polymer Science, Vol. II, New York: Hanser Publishers, MunichVienna 1987. 124 13
3、52null WANG Song(null ) , Ph. D Dissertation of Nanjing University, 19973null YU Xuehai(Z) , XU Jun(null +) , WANG Yugang() , et al. Shiyou Huagong( F) , 1991, 20: 7607644null WANG Zhiliu( ) , WANG Hai(Z) , YAN Xiaohu(k) , et al. Shiyou Huagong( F) , 1992, 21: 22286395 null :? ? &YDSC wL1 COMPARISON
4、 OF DSC TRACES OF POLYSTYRENESSYNTHESIZEDBYANIONICPOLYMERIZATIONWANG Song1, 2, DAI Qingping1, CHENG Rongshi1(Department of Chemistry,Nanjing University,Nanjingnull 2100931,Research Centre of Materials,Beijing Instituteof Technology,Beijing,1000812)Abstractnull Atactic polystyrenes with molecular wei
5、ghts from 460 to 1550000 were studied bycalorimetric measurement. It was found that the samples having molecular weight higher than103 produce initial DSC heating traces with wellnulldefined endothermic peaks in the vicinity ofT g, the peak size decreased with the increase of molecular weight and th
6、en disappeared onrescanning. However, for the samples with molecular weights less than 103 no endotherm wasobserved in the same measurement conditions. The endothermic peaks in DSC traces suggestthe existence of localised regions of segmental order in the samples and its possible originmust be the c
7、ontribution of rr sequence in chains, because these samples have the differentsteric structures. 13CnullNMR determination indicates the proportion of rr triads is lower than20% for samples of Mn 103. Atacticpolystyrenes used in the study were synthesised by solution polymerisation with nnullbutyllithium as initiator, benzene as solvent and alcohol as precipitant. The polymerconcentrations were about 1 2% at the end of polymerisation.Key wordsnull Atactic polystyrene, DSC measurement, Dilute slution640null nullsnull null0null nullnull null1998 M
