Tenhaeff Wyatt E, Gleason Karen K
Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
Langmuir. 2007 Jun 5;23(12):6624-30. doi: 10.1021/la070086a. Epub 2007 Apr 24.
Initiated chemical vapor deposition (iCVD) of alternating copolymer thin films has been achieved for the first time. Copolymerization is desirable for maleic anhydride (Ma) since this monomer does not homopolymerize to an appreciable extent. At conditions where the observed deposition rates for styrene (S) and Ma homopolymers were only 0 and 5.5 nm/min, respectively, combining the two monomers resulted in a much higher deposition rate of 75.4 nm/min. iCVD processes utilize low energy (<30 W) to generate peroxy radicals from initiator molecules while avoiding degradation of functional groups in the monomers. Indeed, full retention of the anhydride functionality from the Ma monomer and avoidance of undesirable side reactions was observed in iCVD of poly(styrene-alt-maleic anhydride) (PSMa) copolymer films. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and 13C nuclear magnetic resonance (NMR) conclusively demonstrate that all of the copolymer films contain 50% styrene and 50% Ma (within experimental error), irrespective of gas feed ratios employed during the deposition. The 13C NMR signal in the 136-140 ppm region from the quaternary carbon in styrene and additional distortionless enhancement polarization transfer experiments confirmed that the copolymers are strictly alternating. Varying the gas feed ratio of Ma to styrene provided control over deposition rates and number-average molecular weights. Number-average molecular weights varied from 1380 to 4680 g/mol, and deposition rates varied from 6.3 to 75.4 nm/min.
首次实现了交替共聚物薄膜的引发化学气相沉积（iCVD）。马来酸酐（Ma）适合进行共聚，因为该单体不会显著地进行均聚。在苯乙烯（S）和Ma均聚物的观测沉积速率分别仅为0和5.5 nm/min的条件下，将这两种单体混合后得到了高达75.4 nm/min的沉积速率。iCVD工艺利用低能量（<30 W）从引发剂分子产生过氧自由基，同时避免单体中官能团的降解。实际上，在聚（苯乙烯-交替-马来酸酐）（PSMa）共聚物薄膜的iCVD过程中，观察到Ma单体的酸酐官能团完全保留，且避免了不期望的副反应。傅里叶变换红外光谱、X射线光电子能谱和13C核磁共振（NMR）确凿地表明，所有共聚物薄膜均含有50%的苯乙烯和50%的Ma（在实验误差范围内），与沉积过程中使用的气体进料比无关。来自苯乙烯中季碳的13C NMR信号在136 - 140 ppm区域以及额外的无畸变极化转移增强实验证实了共聚物是严格交替的。改变Ma与苯乙烯的气体进料比可控制沉积速率和数均分子量。数均分子量在1380至4680 g/mol之间变化，沉积速率在6.3至75.4 nm/min之间变化。
