Self-Organization of Rod-Coil Block Copolymer and Side-Chain Liquid Crystalline Polymer Based on Conjugated Polymer Building Block

張純華(Chun-Hua Chang)

指導教授 ： 陳信龍

國立清華大學/工學院/化學工程學系/碩士(2010年)

摘要

Copolymers composing of rodlike conjugated segments have drawn much attention recently because this class of materials effectively integrate the unique functionality of the conjugated polymer with the self-assembling capability for generating controllable nanostructures. This thesis is dedicated to the study of two types of conjugated copolymers. The first type is the rod-coil block copolymers composing of poly(3-hexylthiophene) (P3HT) as the rod block and poly(methyl methacrylate) (PMMA) as the coil block. The second system is a copolymer called oly (fluorenylstyrene) (PSt-Fln)? composing of a polystyrene backbone attached with conjugated oligomer of 9, 9-di-n-hexyl-2, 7-fluorene (HF) as the side chain. For the former system, we are concerned with the self-organization behavior of P3HT block confined within the discrete microdomains, while for the second system, we center on the conformational structure of this novel type of copolymer in the solution state.

We compared the self-assembly behavior of P3HT block in the PMMA-rich P3HT-PMMA diblock and triblock copolymers. On the basis of similar volume fraction and molecular weight of P3HT block, the crystallizability of P3HT in these copolymers has been examined. In the P3HT-b-PMMA diblock, P3HT confined within the discrete microdomains was essentially uncrystallizable; however, anomalous mesomorphic sub-domains with ca. 5 nm in interdomain distance and two types of  stacking of the thiophene rings were observed. These mesomorphic domains sustained up to ca. 70 oC, which was much lower than the typical melting point of P3HT crystallites. Crystallization of P3HT block was able to occur in PMMA-b-P3HT-b-PMMA triblock copolymer to generate the layer structure as that found in the crystalline homopolymer. The great hindrance to P3HT crystallization in the diblock system was attributed to the strong driving force of the conformational relaxation of the longer PMMA block (comparing to that in the triblock) that prohibited the crystalline packing of P3HT block.

We have examined the conformational structure of PSt-Fln (with n corresponding to the number of HF unit per side chain, n ≤ 3) bearing different side-chain lengths dissolved in THF, toluene, methylcyclohexane (MCH) and cyclohexane (CYH) by means of SAXS. THF and toluene are relatively good solvent for the copolymer and the SAXS profiles reveal that the copolymer chains in these two solvents adopt rodlike conformation irrespective of the side chain length. PSt-Fl1 remained well dispersed in MCH and CYH in spite of their poorer solvent quality. However, PSt-Fl2 and PSt-Fl3 undergo aggregation in these two solvents, giving rise to cylindrical aggregates or bundles. The copolymer chains in the bulk state are found to pack in a pseudo-hexagonal lattice with the rodlike side chains tilt away from the backbone by ca. 60o.

關鍵字

共聚物 ； 硬桿-柔軟段 ； 小角度散射

並列摘要

無資料

並列關鍵字

Rod-Coil block copolymer ； P3HT ； PF

參考文獻

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