Side Chain Liquid Crystalline Polymers Exhibiting Chiral Smectic C Phase

Author : Michael Joseph Rubal
Publisher :
ISBN 13 :
Total Pages : 364 pages
Book Rating : 4.:/5 (82 download)

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Download or read book Laterally Attached Side-chain Liquid Crystalline Polynorbornenes Designed to Exhibit a Chiral Smectic C Phase written by Michael Joseph Rubal and published by . This book was released on 2005 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: "In order to better assign the thermotropic properties of laterally attached side-chain liquid crystalline polymers (SCLCPs), a series of model compounds, {2, 5-bis [(3' -fluoro-4' -n-alkoxyphenyl)ethynyl]phenyl}- alkanes, with spacer lengths m = 2 to 10, and 12 with n-alkoxy substituent lengths of n = 8 and n = 10 were synthezised and compared with previous results of m = 0, 1, and 11.1̕2 The thermotropic behavior of the models were analysed by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). For all model compounds, only a nematic phase was observed. The isotropization temperatute decreased rapidly for the space length m = 0 to 3 and then converged toward a constant value for longer spacer lengths. Interestingly, the n = 8 model compounds were more stable, had a longer isotropization temperature, then the n=10 model compounds for m 8, but the n = 10 model compounds have a higher isotropization temperature than the n = 8 model compounds for m = 8. Ring-openning metathesis polymerization (ROMP) of achiral 5-[[[[2',5'-bis[2-(3'-fluoro-4'-decyloxyphenyl)-ethynyl]phenyl]alkyl]oxy]carbonyl]bicyclo[2.2.1]hept-2-enes were completed for a series of spacer lengths m = 3 to 10, and 12 and gave polymers with a degree of polymerization (DP[subscript n]) of 40 to 167 and polydispersity (pdi) of 1.17 to 1.38. The thermotropic behavior was studied by DSC and POM. For all achiral polymers, only a nematic phase was observed. As with the model compounds, the isotropization temperature rapidly destabilized for m = 1 to 3 and converges to a constant value for longer spacer lengths. Furthermore, there was excellent correlation between the value of athe isotropization temperature of hte models and the achiral polymers. Since the polymer with the short spacer length m = 1 was the only one with a smectic C phase, chiral poly {5-{1-[[[2'',5''-bis[2-(3'-fluoro-4'-decyloxyphenyl)ethynyl]-phenyl]ethyl]oxy]carbonyl}bicyclo[2.2.1]hept-2-ene and poly {5-{1-[[[2'',5''-bis[2-(3'-fluoro-4'-decyloxyphenyl)ethynyl]-phenyl]ethyl]oxy]carbonyl}bicyclo[2.2.1]hept-2-ene-co- 5-{[2',5'-bis[2-(3'-fluoro-4'-decyloxyphenyl-ethynyl]benzyl]oxy]carbonyl}bicyclo[2.2.1]hept-2-ene} were synthesized by ROMP and gave polymers in high yield. The homopolymer has a DP[subscript n] = 21 and a pdi of 1.13. The copolymer had a DP[subscript n] = 95.4 and a pdi of 1.36. The thermotropic behavior was studied by DSC and POM. The homopolymer showed no liquid crystallinity, just a glass transition at 38.7 °C. The copolymer was able to restablish the liquid crystallinity, however only nematic textures were present"-P. iii-v.