科研之友
微信
新浪微博
Facebook
分享链接
摘要
The reversible addition-fragmentation chain transfer (RAFT) polymerization of N-acryloyl morpholine (NAM), a water-soluble bisubstituted acrylamide derivative, has been investigated in the presence of tert-butyl dithiobenzoate (tBDB), a chain transfer agent (CTA) which showed good fragmentation/reinitiation efficiency as reported in a previous comparative study. The influence of several experimental parameters, such as temperature, monomer concentration [AT], dithioester to initiator molar ratio ([CTA]/[AIBN]) and monomer to dithioester molar ratio ([M]/[CTA]), has been studied with respect to polymerization duration, conversion limit, adequacy between experimental and calculated molecular weight (MW) values and polydispersity index (PDI). The kinetics has been followed over the whole conversion range by 1H NMR spectroscopy and the MW determined by aqueous size exclusion chromatography with on-line light scattering detection. This study evidences the preponderant parameters leading to an excellent control of MW and PD1. Kinetics appear strongly influenced by both temperature and [CTA]/[AIBN] ratio, and to a lesser extent by monomer concentration. A high [CTA]/[AIBN] ratio resulted in a long induction time, which could be reduced by replacing the CTA by a macroCTA. Surprisingly, the control over MW and PDI was improved by an increase in temperature from 60 to 90 degreesC. Moreover, an increase of the [CTA]/[AIBN] molar ratio from 3.3 to 10, also improved the MW control; however, an additional increase of this ratio to 20 led to a marked loss of control, indicating the existence of an optimal [CTA]/[AlBN] ratio. In addition, MALDI-TOF MS and (1)H NMR analyses confirmed the end-functionalization of the chains with a dithiobenzoate group.
- 出版日期2004-12-9
