Thermally stimulated current studies of molecular dynamics in liquid crystalline polymers

• Main Authors: Chang,Huey-Ling, 張惠玲
• Other Authors: Hsu,Chain-Shu
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/95229647983771287440

博士 === 國立交通大學 === 應用化學研究所 === 85 === Thermally stimulated current and relaxation map analysis (TSC/RMA) are used to study the molecular dynamics of main-chain and side-chain liquid crystalline(LC) polymers. In the frist series of side-chain liquid crystalline copolysil-oxanes, the dual glass transitions as well as effect of spacer length, polymer backbone and lateral substitution on the molecular dynamics, are investigated byTSC/RMA. The results demonstrate that a longer spacers, a more flexible polymerbackbone and a smaller lateral subsitituent will lead easier moving of the sidegroup molecules. In the second series of ferroelectric side-chain LC polyoxetanes , the glass transition, side-chain motions as well as ferroelectric propertiesof the obtained polymers are studied by TSC/RMA. The results demonstrate that ferroelectric mode, i.e. Goldstone mode, can not be observed in the TSC measure-ment. TSC/RMA are used to study the third and forth series of side-chain LC poly-methacrylates and polyacrylates. All of the LC polymethacrylates and polyacrylatesreveal a glass transition and a depolarization peak which is attributed to the motions of the longitudinal components of the dipole moment of the longitudinalcomponents of the dipole moment of the mesogenic side groups on the TSC curves. All obtained LC polymethacrylates show a glass transition temperature lower than that of poly(methyl methacrylate) and all obtained LC polyacrylates presenta glass transition higher than that poly(methyl acrylate). The results indicatethat the side group has prominent effect on the glass transition temperature. The glass transition is generally difficult to be observed in the DSC measure-ments. The glass transition as well as molecular dynamics of some main-chain LCpolymers are investigated by TSC/RMA also. In the fifth series of LC polyesterswhich containing the 4-hydroxy-3,5-dibromobenzoic acid monomer, their glass tran-sition are observed on the TSC curves. The results demonstrate that introducingthe 4-hydroxy-3,5-dibromobenzate unit into the rigid-rod polyesters decreasesthe melting points and glass transition temperatures of the obtained copolyesters. The TSC is also used to study the glass transition of a series of LC polyestersand their block copolymers with polyether sulfone. The LC polymers which displayno glass transition on the DSC scans, however, reveal very clear glass trasition on TSC curves. The block copolymers of LC polyesters and polyether sulfone whichdisplay very broad glass transition DSC curves, show very sharp glass transitionpeaks on the TSC curves. The results indicate that TSC is a very useful techniqueto study the glass transition of the main-chain LC polymers