Synthesis and properties of cationic photopolymerizable hyperbranched polyesters with terminal oxetane groups by the couple-monomer polymerization of carboxylic anhydride with hydroxyl oxetane
✍ Scribed by Fu Zhan; Anila Asif; Jianhua Liu; Hailong Wang; Wenfang Shi
- Publisher
- Elsevier Science
- Year
- 2010
- Tongue
- English
- Weight
- 670 KB
- Volume
- 51
- Category
- Article
- ISSN
- 0032-3861
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✦ Synopsis
The hyperbranched polyesters with terminal oxetane groups were synthesized via couple-monomer methodology based on carboxylic anhydride and hydroxyl oxetane. Two competitive reactions, ringopening reaction of carboxylic group with oxetane group and esterification of carboxylic group with hydroxyl group, occurred synchronously during the polymerization. The results showed that the hyperbranched polyesters, poly(SA-EHO) and poly(SA-EHPO), were synthesized successfully when succinic anhydride (SA) was selected to react with 3-Ethyl-3-(hydroxymethyl)oxetane (EHO) and 3-ethyl-3-((4-hydroxymethyl)phenoxymethyl)oxetane (EHPO), respectively. The degree of branching was determined to be about 0.7 for poly(SA-EHO) from the 1 H NMR result, which was higher than those reported in literature, indicating that the esterification was dominant. The glass transition temperatures (T g )s were measured as À11.5 C for poly(SA-EHO) and 14.3 C for poly(SA-EHPO) by DSC. The number average molecular weights were 1914 g/mol and 2108 g/mol with the polydispersity indices of 2.39 and 2.28 for poly(SA-EHO) and poly(SA-EHPO), respectively. Both poly(SA-EHO) and poly(SA-EHPO) were added to bisphenol A epoxy resin, EP828, with different contents and cured under UV exposure. From the DMTA and tensile results, the UV cured poly(SA-EHPO) showed higher T g and tensile strength compared with poly(SA-EHO) because of the existence of phenyl group in poly(SA-EHPO) chain. Moreover, both the T g s and mechanical strength decreased, whereas the elongation percents at break increased with poly(SA-EHO) and poly(SA-EHPO) increased. This indicates that the flexibility of cured films was improved by the addition of poly(SA-EHO) and poly(SA-EHPO) in the formulations.