Polymers at interfaces: Using atom transfer radical polymerization in the controlled growth of homopolymers and block copolymers from silicon surfaces in the absence of untethered sacrificial initiator
Polymers at interfaces: Using atom transfer radical polymerization in the controlled growth of homopolymers and block copolymers from silicon surfaces in the absence of untethered sacrificial initiator
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DOI：
10.1021/ma991146p
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发表时间：
1999-12-28
期刊：
影响因子：
5.5
通讯作者：
Pakula, T
中科院分区：
文献类型：
--
作者：
Matyjaszewski, K;Miller, PJ;Pakula, T
以2-溴异丁酸酯片段为引发剂，在硅晶片表面进行苯乙烯和丙烯酸酯的原子转移自由基聚合。在存在的适当比例的活化和钝化过渡金属物种，苯乙烯的受控自由基聚合进行了观察，使得从表面生长的链组成的层的厚度与在溶液中聚合的链的分子量在相同的，但单独的，实验线性增加。层厚度随苯乙烯和丙烯酸甲酯的ATRP的反应时间线性增加，这是由于相对于单体的极低引发剂浓度和低单体转化率。通过从聚苯乙烯层聚合丙烯酸甲酯或丙烯酸叔丁酯的嵌段观察到控制的进一步证据。表面层的亲水性的改性通过聚（苯乙烯-b-丙烯酸叔丁酯）水解成聚（苯乙烯-b-丙烯酸）来实现，并且通过水接触角从86度减小到18度来证实。ATRP在聚合过程中的机制方面证实了在纯铜（II）络合物的存在下，非常厚的聚苯乙烯膜的生长。因为没有去激活器。存在时，金属络合物仅用于通过氧化还原过程促进引发。在这些膜中，在受控条件下用丙烯酸甲酯扩链的尝试是不成功的。表面层的聚合的模拟表明更广泛的分子量和链端分布，确认XPS结果上的溴吸收强度的逐步降低。
The atom transfer radical polymerization (ATRP) of styrene and acrylates from silicon wafers modified with an initiator layer composed of 2-bromoisobutyrate fragments is described. In the presence of the proper ratio of activating and deactivating transition-metal species, controlled radical polymerizations of styrene were observed such that the thickness of the layer consisting of chains grown from the surface increased linearly with the molecular weight of chains polymerized in solution in identical, yet separate, experiments. The layer thickness increased linearly with reaction time for ATRP of styrene and methyl acrylate due to both the extremely low initiator concentration relative to monomer and the low monomer conversion. Further evidence for control was observed by the polymerization of blocks of either methyl or tert-butyl acrylate from the polystyrene layer. Modification of the hydrophilicity of the surface layer was achieved by hydrolysis of the poly(styrene-b-tert-butyl acrylate) to poly(styrene-b-acrylic acid) and confirmed by decrease in water contact angle from 86 degrees to 18 degrees. The mechanistic aspects of ATRP in the polymerization process were confirmed by the growth of very thick polystyrene films in the presence of a pure copper(II) complex. Since no deactivator. was present, the metal complex served only to facilitate initiation by a redox process. Attempts to extend chain with methyl acrylate under controlled conditions were unsuccessful in those films. The simulation of polymerization of surface layers suggests broader molecular weight and chain end distributions, confirming XPS results on the progressive decrease of Br absorption intensity.