摘要
本研究首次嘗試利用液態乳酸寡聚物直接在13.56MHz的射頻電漿中進行凝態電漿聚合反應，且證實不論乳酸寡聚物分子量大小或改變電漿功率，皆可以成功製備固態的凝態電漿聚乳酸。在固態膜對於低分子量乳酸寡聚物的可穿透性實驗中，驗證液態乳酸寡聚物分子可溶脹進入表層初形成之固態膜，再藉於表面受電漿直接活化而鍵結上固態膜，最終形成厚度達微米尺度的凝態電漿聚乳酸。聚合過程無需使用溶劑或催化劑，簡化並加速了聚乳酸的製備。利用傅立業紅外線光譜儀及固態核磁共振儀分析化學結構，顯示凝態電漿聚乳酸可有效保留乳酸官能基，同時有交聯及Norrish-type II反應發生，形成以線性聚乳酸為主並具有-CH2-及C=C-C=O的結構。將寡聚物的分子量提高，研究中發現可使交聯密度由10-4 g/cm3降低至10-5 g/cm3，但反應時間也較長，且過高的分子量會造成聚合障礙。而降低電漿功率也可降低對液態寡聚物造成的結構破壞，但同時所需反應時間也較長。此外，水解實驗結果顯示凝態電漿聚乳酸在95℃的去離子水中7天可降解70%，而不易降解的30%為具交聯結構的固態膜。藉凝態電漿聚合法在低於100℃反應溫度時，可得到與傳統直接縮合聚合在近200℃反應時相當的反應速率常數(10-5~10-3 L/sec*mole)，顯示本研究提供一嶄新且更有效率的凝態電漿聚乳酸合成方式。
並列摘要
Directly starting from liquid phase L-lactic acid (LLA) or its oligomer, the condensed-phase plasma polymerized poly(L-lactic acid) (PLLA) was for the first time successfully synthesized via in-situ plasma in radio frequency (RF) at 13.56 MHz. The polymerization process is based on the permeability of the initially polymerized crosslinking film to liquid LLA oligomer. As swelling into the film, LLA oligomer bonded on the film surface as a result of direct plasma activation and terminated in macro-scale bulk. The chemical structure was characterized by fourier-transform infrared spectroscopy (FTIR) and solid state nuclear magnetic resonance (solid state NMR). Based on this multitechnique analysis, it was determined that condensed-phase plasma polymerized PLLA retained original functionalities of LLA; moreover, it contained methylene and enone which were absent from linear PLLA. Those could be explained by crosslink and Norrish-type II reaction. Increasing molecular weight of oligomer reduced the crosslink density from 10-4 g/cm3 to 10-5 g/cm3; however, it not only took longer reaction time, but obstructed reaction with exceed high oligomer. Structure was more regular for treating at low power, when compared at completely solidified phase, and reaction time at 50W took 6 times than at 200W. Besides, 70% of condensed-phase plasma polymerized PLLA hydrolyzed in distilled water at 95℃ in a week, and the other 30% remained through crosslink. This novel one-step, solvent-free and low temperature method had the same reaction constant(10-5~10-3 L/sec*mole) as traditional one at high temperature, thus was an alternative route to the synthesis of bulk PLLA.