ISSN:
1022-1352
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
A kinetic study of the γ-ray polymerization of three mesogenic diacrylates, 4,4′-bis(3-acryloyloxypropoxy)biphenyl (DAPB), 4,4′-bis(6-acryloyloxyhexyloxy)biphenyl (DAHB) and 4,4′-bis(11-acryloyloxyundecyloxy)biphenyl (DAUB), is presented. All compounds were studied on their polymerizability in the crystalline state. It was found that they can be completely polymerized though the reaction rates are very different and increase with increasing length of the alkylene spacer unit. Up to moderate conversion, solid-state polymerization is comparable with that of acrylamide and follows a t2 rate law. DAPB was chosen for a detailed kinetic study of the in-source and post-polymerization in the crystalline, liquid crystalline and liquid phase. In-source polymerization is complete in the various phases though reaction rates and curve shapes of dose vs. conversion curves are very different. Possible origins such as enhanced molecular diffusion at elevated temperatures are discussed. X-ray studies indicate that a well-ordered polymer can be obtained from polymerization in a smectic phase, while polymers obtained from a crystaline or melt phase are considerably less ordered. Post-polymerization was studied as a function of the radiation dose and the temperature of the subsequent annealing process. It was found that the limiting conversion increases with increasing radiation dose and temperature of the annealing process, but the polymerization is always incomplete. Even post-polymerization in the melt phase does not exceed 55 percent conversion. The post-polymerization behaviour is comparable with that of acrylamide and can be described by a linear relation between conversion and annealing time t.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/macp.1996.021970305
