The Structure and Properties of Ultra-high density Polymer Brushes

超高密度聚合物刷的结构与性能

• 批准号: 12450385
• 负责人: FUKUDA Takeshi
• 金额: $ 10.82万
• 依托单位: KYOTO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12450385/
• 关键词: high-density polymer brush; swollen graft film; dry graft film; plate compressibility; non-scaling; glass transition temperature; surface properties; bulk properties; ポリマーブラシ; 超高密度ブラシ; 単分散ポリマーブラシ; リビングラジカル重合; 高伸長ブラシ; 高弾性ブラシ; AFM; フォースカーブ

Living radical polymerizations (LRPs) such as atom transfer radical polymerization (ATRP) and reversible addition-fragmentation transfer (RAFT) polymerization were applied to various solids (silicon wafer, polymer films, silica or metal nano-particles, etc.) with initiating sites chemically bound on their surfaces, establishing experimental techniques to prepare graft polymer films (polymer brushes) of differing monomers with controlled chain length and chemical structure and with a surface density as high as 0.7 chains/nm^2.These graft films were recognizable as a new molecular organization having characteristic properties, in both swollen and dry states, different from those of the equivalent cast films. For example, the polymer chains in the high-density film swollen by a good solvent are highly extended normally to the film surface, thus giving a film thickness of 80 to 90% of the fully stretched chain length. The plate compressibility of the swollen graft film disobeys the scaling theory, and that of the dry (melt) film is about 50% larger than the cast film. Moreover, the glass transition temperature T_g of the dry graft film is essentially different from that of the equivalent cast film in both low-molecular weight (film thickness < 50nm) and high-molecular weight regions. In particular, the experimental data indicate that the Tg of poly(methyl methacrylate) (PMMA) high-density graft films is about 8K higher than that of bulk PMMA even in the limit of high molecular weight, meaning that the high-density grafting has an effect not only to thin films but also to thick films and hence to the bulk of the films.

活性自由基聚合（LRP），如原子转移自由基聚合（ATRP）和可逆加成断裂转移（RAFT）聚合被应用于具有引发位点的各种固体（硅片、聚合物薄膜、二氧化硅或金属纳米颗粒等）化学键合在其表面，建立了实验技术来制备不同单体的接枝聚合物薄膜（聚合物刷），这些单体具有受控的链长和化学结构，并且表面密度高达0.7链/nm^2。接枝膜被认为是一种新的分子组织，在溶胀和干燥状态下都具有与同等流延膜不同的特性。例如，用良溶剂溶胀的高密度薄膜中的聚合物链垂直地高度延伸到薄膜表面，从而得到完全拉伸链长度的80%至90%的薄膜厚度。溶胀接枝膜的板压缩率不符合缩放理论，干（熔）膜的板压缩率比流延膜大约50%。此外，干接枝膜的玻璃化转变温度T_g在低分子量（膜厚<50nm）和高分子量区域均与同等流延膜有本质不同。特别是，实验数据表明，即使在高分子量的极限下，聚甲基丙烯酸甲酯（PMMA）高密度接枝薄膜的Tg也比本体PMMA高约8K，这意味着高密度接枝具有不仅对薄膜有影响，而且对厚膜也有影响，因此对大部分薄膜也有影响。