聚乳酸與幾丁質合成功能性高分子材料之研究

Abstract

具生物相容性和生物降解性的功能性高分子被認為是在可分解塑膠中具潛力的選擇;然而，目前仍很少有相關的實用產品出現在生物醫藥和塑膠產業中。本論文研究重點著重在天然高分子的合成製備與其物理性質討論，尤其是甲殼素為主的多醣和聚乳酸所合成的功能性高分子材料。 在這項研究中，新的溫感型幾丁質基聚氨酯（TRCPUs）被設計出具有隨溫度變化的溶膠 - 凝膠轉變特性。這類的有機凝膠，由異佛爾酮二異氰酸酯（IPDI），聚乙二醇（PEG）和甲殼素所組成，在有機溶劑中具有隨溫度變化的溶膠 - 凝膠特性，由於其軟鍊段和硬鍊段之間的相互作用。在極性有機溶劑中聚乙二醇為主的TRCPUs軟鍊段具有熱黏彈性和親水性的特點。此外，在相同的製程中，類似TRCPUs有機凝膠被觀察其具有凝膠到固體轉變的特性，期轉變特性將進一步在此論文中討論。此含有甲殼素的凝膠共聚物是透過共價鍵結合的聚氨酯有機凝膠，在低溫注射中約在105°C時會有凝膠到固體轉變的特性。此TRCPUs的結構與熱行為由NMR，FTIR和DSC進行了鑑定，並討論其在有機溶劑中的流變行為。 另一方面，在這項研究中，我們提出了一個新的合成方法，創造新的聚氨酯，合成可生物降解的脂肪族聚酯，此材料具有良好的機械性能。乳酸（LA）和乙二醇（EG）聚合成聚（乳酸）多元二醇（PLA-OHS），此反應不使用催化劑直接在溶劑與起始劑直接進行縮聚反應。兩種不同的異氰酸酯，4,4 - 二苯基甲烷二異氰酸酯（MDI）與2,4 - 甲苯二異氰酸酯（TDI），被用來製備具適當的機械強度與可生物降解的聚乳酸材料。 1,4 - 丁二醇（BD）和三羥甲基丙烷（TMP）在反應過程中適度的添加以加強其機械強度，並延長聚乳酸聚胺酯的高分子鏈。其中以MDI二異氰酸酯系列中含20％的PBA擁有較好的機械性質，其機械性能明顯優於其他聚乳酸聚胺酯材料。其拉伸強度為46±1.7 MPa而斷裂伸長率是12±0.6％。降解研究結果顯示PLA - PU可以通過改變分子結構與改變環境控制達成生物降解的效果。

It is usually expected that the functional polymers with biocompatibility and biodegradability are the potential candidates in the category of application in compostable plastic industry; however, there are few practical products available on the biomedical and plastic markets. This dissertation was focused on the preparation of functional polymers from natural source and the discussion on their physical behaviors. Both of chitin base polysaccharide and polylactide were used to synthesis the functional polymer. In this research, the new thermal-responsive chitin-based polyurethanes (TRCPUs) have been designed and developed that undergo a sol-to-gel transition with temperature changes. These TRCPUs organogel, composed of isophorone diisocyanate (IPDI), polyethylene glycol (PEG) and chitin, owned the ability to undergo temperature-dependent sol-to-gel transition in organic solvent due to the interaction between soft segments and hard segments. PEG dominated the soft segments of the TRCPUs and imparted the thermoelastomeric and hydrophilic characteristics to the TRCPUs in polar organic solvent. Furthermore, the similar TRCPUs organogel were synthesized in the same process while their gel-to-solid transition was observed and further discussed. Chitin was incorporated into polyurethane via covalent bonding; the resultant copolymer was an injectable organosol at low temperatures that transformed to a semisolid organogel at approximately 105°C. The TRCPUs were characterized by 1H-NMR, FT-IR and DSC, and the rheological behavior of the TRCPU solutions in organic solvents was studied. On the other hand, in this study, we propose a rational synthesis method to create novel poly(ester urethanes) that incorporate biodegradable aliphatic polyester and good mechanical properties of molecular weight advancement and cross-linked network formation. Lactic acid (LA) and ethylene glycol (EG) were polymerized to poly(lactic acid) diols (PLA-OHs) using the direct polycondensation without catalysts, solvent and initiators. Both 4,4-diphenylmethane diisocyanate (MDI) or toluene 2,4-diisocyanate (TDI), were applied to build biodegradable segmented PLA-PUs with appropriate mechanical strength. Appropriate amounts of 1,4-butanediol (BD) and trimethylolpropane (TMP) were added to improve the mechanical strength by extending the molecular chain of the PUs. Among the PLA-OHs, a PLA/PBA-PU of the MDI diisocyanate series with 20 wt%PBA displayed mechanical properties markedly superior to the other polymers. Its tensile strength was 46 ± 1.7 MPa and its elongation at break was 12 ± 0.6%. Results of the degradation study demonstrated that the recoverability of PLA-based PUs could be controlled by changing the molecular components and degradable environment.