利用beta-環狀糊精/聚醚分子間的 超分子自組裝製備準聚輪烷膠體

Abstract

本研究利用beta-環狀糊精(beta-cyclodextrin, beta-CD)與聚醚(polyether)之間連續形成包藏錯合物(inclusion complexes, ICs)的機制，製備準聚輪烷(polypseudorotaxane, PPR)超分子自組裝(supramolecular self-assembling)膠體。研究的第一部分在不同反應條件下嘗試製做PPR膠體，透過產物結晶結構之鑑定及內部組織形態之觀察，篩選出成功形成PPR膠體的樣品，並探討影響PPR膠體生成與否的因素。反應的操控變因包括：聚醚分子的種類(聚乙二醇(polyethylene glycol, PEG)或PEG與聚丙二醇(polyprolyene glycol, PPG)之共聚物PPG-PEG-PPG, reverse Pluronic®)、溶劑種類(水、30及60% (v/v) DMSO水溶液或140 mg/mL檸檬酸水溶液)以及反應溫度(25或65℃)。第二部分則針對前段實驗所篩選出之PPR膠體，進一步分析其流變性質及內部的PPR結晶粒子大小，以連結膠體之配方製程、內部結構與流變性質三者間的關係。根據第一部分的實驗結果，可形成PPR膠體的條件有三種：beta-CD與reverse Pluronic®在水或在檸檬酸水溶液中於25℃反應(beta-CD/RPL-W-25、beta-CD/RPL-C-25)，或在水中於65℃反應(beta-CD/RPL-W-65)。所形成的三種PPR膠體皆具有通道型(channel-type)結晶結構及網狀組織，但beta-CD/RPL-W-25內部含有許多未溶解的beta-CD顆粒，不如另二種膠體般均勻。而網狀組織的緻密程度以beta-CD/RPL-C-25最高。以PEG為高分子所製備的樣品，雖然都無法形成穩定明顯的通道型結晶結構，但beta-CD與PEG在65℃的水中反應可錯合形成PPR超分子。第二部分的實驗結果在流變性質方面，三種PPR膠體皆具有搖變減黏(thixotropic)性質，但在結構強度和搖變減黏呈度上相異，以beta-CD/RPL-C-25最高，此膠體經過攪動並長時間靜置後的穩定性也最高。在結晶粒子大小方面，beta-CD/RPL-W-65及beta-CD/RPL-C-25雖同屬結構均勻的膠體，但前者製程經過高溫反應，所生成PPR結晶粒子較大，因而結晶聚集區較大，整體結構較疏鬆，此結構上的差異說明了beta-CD/RPL-W-65何以在強度、搖變減黏性或長時間儲存的穩定度都低於beta-CD/RPL-C-25的原因。

Supramolecular self-assembling gels of polypseudorotaxane (PPR) were made through sequential host-guest inclusion complexations between beta-cyclodextrin (beta-CD) and polyethers. In the first part of this study, beta-CD and the polyethers were mixed and allowed to react under different conditions. The controlled variables included polyether species (PEG or a copolymer PPG-PEG-PPG named reverse Pluronic®, where PEG and PPG were polyethylene glycol and polyprolyene glycol, respectively), solvent types (water, 30 or 60% (v/v) DMSO(aq) or 140 mg/mL citric acid(aq)), and reaction temperatures (25 or 65℃). Crystal morphologies and internal micro-structures of the resulting products were observed to identify the formation of PPR gels. Effects of reaction conditions on the gel formation were discussed. In the second part of this study, PPR gels were prepared according to the proper conditions obtained from the first part. Rheological properties and size of PPR crystallites in the gels were analyzed to connect the relationships between preparation conditions, internal structures and gel rheology. The proper conditions for PPR gel formation were: beta -CD/reverse Pluronic® reacted in water or in citric acid(aq) at 25℃ (beta-CD/RPL-W-25、beta-CD/RPL-C-25) or in water at 65℃ (beta-CD/RPL-W-65). The three PPR gels all had channel-type crystalline and net-like structures, while beta -CD/RPL-W-25 contained insolubilized beta-CD particles thus was less homogeneous then the other two. Beta-CD/RPL-C-25 showed the finest net-like structures. Samples prepared from PEG were unable to form evident and stable PPR crystalline. However, reaction in water at 65℃ promoted the formation of PPR supramolecules from beta-CD and PEG。The three PPR gels prepared in this study were all thixotropic, while the gel strength and thixotropy varied among samples, in which beta-CD/RPL-C-25 had the highest value. This gel also showed the highest stability after stirring and long-time storage. As compared with beta-CD/RPL-C-25, the size of PPR crystallites in the high-temperature derived beta-CD/RPL-W-65 was larger, leading to larger domains of crystallite aggregation. This explained why beta-CD/RPL-C-25 and beta-CD/RPL-W-65 were both homogeneous while the latter had lower gel strength, thixotropy and stability after long-time storage.