Nanostructuring Polymers with Cyclodextrins

polycarbonate;styrene;solid state complexation;polystyrene;stereoregularity;polymerization;blend;thermal degradation;miscibility;Poly(methyl methacrylate);poly(vinyl acetate);inclusion compound;cyclodextrin

Uyar, Tamer ; Richard Kotek, Committee Member,C. Maurice Balik, Committee Member,Alan E. Tonelli, Committee Chair,Juan P. Hinestroza, Committee Member,Uyar, Tamer ; Richard Kotek ; Committee Member ; C. Maurice Balik ; Committee Member ; Alan E. Tonelli ; Committee Chair ; Juan P. Hinestroza ; Committee Member

University:North Carolina State University

关键词: polycarbonate;    styrene;    solid state complexation;    polystyrene;    stereoregularity;    polymerization;    blend;    thermal degradation;    miscibility;    Poly(methyl methacrylate);    poly(vinyl acetate);    inclusion compound;    cyclodextrin;   

Others  :  https://repository.lib.ncsu.edu/bitstream/handle/1840.16/4047/etd.pdf?sequence=1&isAllowed=y

美国|英语

来源: null

【 摘 要 】

The formation of polymer-cyclodextrin inclusion compounds of polycarbonate (PC), poly(methylmethacrylate) (PMMA) and poly(vinylacetate) (PVAc) guests with host γ-cyclodextrin (γ-CD) have been successfully achieved. Coalesced bulk polymer samples were obtained by removal of γ-CD from their inclusion compounds (ICs). Spectroscopic findings indicated that the chain conformations of the bulk polymers were altered when they were included inside the CD channels and extended chain conformations were retained when coalesced from their ICs. Significant improvements were observed in the thermal transitions for the coalesced polymers, with glass transitions shifted to higher temperatures. Thermal studies reveal that the thermal stabilities of coalesced polymers increased slightly compared to the corresponding as-received polymers and degradation products of the polymers are affected once the polymers chains are included inside the γ-CD-IC cavities. A procedure for the formation of intimate blends of binary and ternary polymer systems; PC/PMMA, PC/PVAc, PMMA/PVAc and PC/PMMA/PVAc was studied. PC/PMMA, PC/PVAc, PMMA/PVAc and PC/PMMA/PVAc were included in γ-CD channels and were then simultaneously coalesced from their common γ-CD-ICs to obtain intimately mixed blends. It was observed that the ratios of polymers in coalesced blends were significantly different than the starting ratios, and PC was found to be preferentially included in γ-CD channels when compared to PMMA or PVAc. Physical mixtures of polymer blends were also prepared by co-precipitation and solution casting methods for comparison. The analysis indicates that the ternary and the binary blends of these polymers achieved by coalescence from their common γ-CD-IC results in a homogeneous polymer blends, possibly with improved properties, whereas co-precipitation and solution cast methods produced phase separated polymer blends. It was shown that coalescence of two or more normally immiscible polymers from their common CD-ICs appears to be an applicable method for obtaining well-mixed, intimate blends.The solid complex of guest styrene included inside the channels of host γ-cyclodextrin (styrene/γ-CDchannel-IC) was formed in order to perform polymerization of styrene in a confined environment (γ-CD channels).Modeling of polystyrenes (PS) with various stereosequences in the narrow cylindrical channels corresponding to those found in γ-CD ICs has been conducted. It was calculated that only isotactic PS stereoisomers can fit into the γ-CD cavity. Thus, based on the modeling of stereoisomeric PSs in narrow γ-CD channels, it was suggested that polystyrene with unusual microstructures might be produced via constrained polymerization of styrene monomer in its γ-CD-IC crystals. The in situ polymerization of styrene inside the narrow channels of its γ-CD-IC crystals was performed in aqueous media. Alternatively, the solid-state polymerization of styrene/ϒ-CD IC has also been carried out by radiation polymerization. It was found that most styrene monomer migrates from the γ-CD channels and polymerizes outside of the channels. Yet, a rotaxaned structure has been obtained where some CD molecules entrapped along the PS chains after the polymerization.