CAJ | 학술논문

聚乳酸(PLA)是一种环境友好及生物可降解的聚合物，其界面性质受到了广泛关注.本文以Langmuir-Blodgett (LB)膜天平、原子力显微镜(AFM)研究了聚(L-乳酸)(PLLA)在气液界面上的性质.表面压-面积(π-A)等温曲线的结果表明，在膜压缩的初始阶段，表面压逐渐增大；当膜压为9.0 mN?m-1时，曲线出现了一个平台，其重复单元的面积大约在0.11-0.17 nm2之间.原子力显微镜的结果发现，在压缩过程中，膜结构发生了明显的变化：平台刚出现时，膜内出现了大量的纤维结构；在平台区内，界面上出现了多层膜结构.特别地，当表面压为20.0 mN?m-1时， PLLA在界面上可形成约6.0 nm厚的薄膜.由此可见， PLLA等温线中的平台与其膜结构的变化紧密相关.这有别于普通双亲分子的性质，即这类双亲分子π-A等温线中的平台通常表示它们在二维空间上发生了单分子膜的相转变.
취유산(PLA)시일충배경우호급생물가강해적취합물，기계면성질수도료엄범관주.본문이Langmuir-Blodgett (LB)막천평、원자력현미경(AFM)연구료취(L-유산)(PLLA)재기액계면상적성질.표면압-면적(π-A)등온곡선적결과표명，재막압축적초시계단，표면압축점증대；당막압위9.0 mN?m-1시，곡선출현료일개평태，기중복단원적면적대약재0.11-0.17 nm2지간.원자력현미경적결과발현，재압축과정중，막결구발생료명현적변화：평태강출현시，막내출현료대량적섬유결구；재평태구내，계면상출현료다층막결구.특별지，당표면압위20.0 mN?m-1시， PLLA재계면상가형성약6.0 nm후적박막.유차가견， PLLA등온선중적평태여기막결구적변화긴밀상관.저유별우보통쌍친분자적성질，즉저류쌍친분자π-A등온선중적평태통상표시타문재이유공간상발생료단분자막적상전변.
Poly(lactic acid) (PLA) has attracted considerable interest as an environmental y friendly and biodegradable polymer. The properties of poly(L-lactic acid) (PLLA) at an air/water interface were studied based on the Langmuir-Blodgett (LB) film balance and atomic force microscopy (AFM). The surface pressure-area (π-A) isotherm indicated that the surface pressure of PLLA initial y increased as the interfacial film was compressed;atπ=9.0 mN?m-1, a plateau was observed in theπ-A isotherm, in which the area of the repeat unit was in the approximate range 0.11-0.17 nm2. The AFM results showed that there is a clear structural transition in the PLLA film during the compression:(i) at the beginning of the plateau, a number of fibrils are present at the air/water interface and (i ) multilayer structures (at least bilayer, i.e., the underlying layer and top layer consisting of fibrils) is formed in the plateau region. In particular, whenπ=20.0 mN?m-1, a thin film of PLLA of thickness about 6.0 nm was fabricated. Our findings suggest that the plateau in the PLLAπ-A isotherm is closely related to a change in the film structure from monolayer to multilayer at the air/water interface. This is significantly different from the behavior of conventional amphiphiles, because the plateau in amphiphilesπ-A isotherm is equivalent to a phase transition of monolayers derived from amphiphiles in a two-dimensional plane.