原子轉移自由基聚合應用於奈米矽片接枝高分子及其介面、螢光感測、抗菌性質之探討

Studies on Polymers Grafting from Exfoliated Silicate Nanoplatelets via Atom Transfer Radical Polymerization and Applications of Surface Properties, Fluorescent Sensors and Antibacterial Abilities

林筱筑(Hsiao-Chu Lin)

指導教授 ： 林江珍

國立臺灣大學/工學院/高分子科學與工程學研究所/博士(2015年)

https://doi.org/10.6342/NTU.2015.10972

摘要

本研究主要在於探討利用酯化反應及麥克加成反應製備新穎的起始劑，並再以溶膠–凝膠法進行共價鍵結於脫層型奈米矽片上，進一步利用原子轉移自由基聚合法將高分子接枝於奈米矽片製備新型奈米複合材料。研究分為三部分：（1）製備新型雙親性複合材料矽片－聚異丙基丙烯醯胺並探討其界面性質的變化。（2）導入奈米銀粒子於矽片－聚異丙基丙烯醯胺中，利用其溫度感應性質對於不同細菌的抗菌或偵測研究。（3）製備矽片－聚六乙基甲基丙烯酸酯並導入具螢光之化合物作為螢光偵測細菌之新型複合材料研究。以上各部分主要探討如下：
第一部分為將高分子聚異丙基丙烯醯胺接枝於奈米矽片製備新型雙親性奈米複合材料。研究中發現由於高分子與矽片有親疏水差異因而造成如同界面活性劑的界面現象，而製備不同接枝密度或改變起始劑之結構會影響分子間或分子內作用力的變化，進而改變其界面性質。當高分子接枝密度大時，因為分子間團聚力較大導致臨界微胞濃度上升。而改變起始劑接枝構型由一個變為兩個接枝點時，也會造成高分子間團聚力提高而使臨界微胞濃度上升。此研究利用表面張力、粒徑測量觀察其差異，同時藉由分子模擬亦可證明其結果。
第二部分是將還原奈米銀粒子於矽片－聚異丙基丙烯醯胺中。由結果顯示銀粒子大小具均一性約8奈米且穩定貼附於矽片表面，此結果可經由TEM觀察。銀粒子/矽片－聚異丙基丙烯醯胺中仍保有最低臨界溶解溫度32－33 oC，可由UV-vis及DSC觀察。利用此複合材料的溫感特性，可以用來辨識格蘭氏陽性菌及陰性菌的不同。在高於最低臨界溶解溫度的37 oC時，複合材料較為疏水所以容易與表面疏水的格蘭氏陰性菌親和，反之，當溫度為28 oC時複合材料轉為親水性而與表面親水的格蘭性楊氏菌親和。此結果在抗菌及表面增強拉曼光譜可以驗證。此新型複合材料可作為偵測不同細菌之研究。
第三部分是延續第一部分之合成方法製備矽片－聚六乙基甲基丙烯酸酯。利用縮合反應將具有螢光之化合物鍵結於高分子鏈段製備出新型具有螢光性質的奈米複合材料。利用矽片表面的離子與細菌間的物理捕捉效應，進而可以利用螢光的強弱變化偵測細菌含量。由SEM可以觀察矽片貼附於細菌表面。利用離子交換法改質矽片所製備之螢光矽片則因為離子交換之螢光化合物無法穩定接於矽片上，而無法有效利用於細菌的偵測。由螢光光譜可以觀察兩者螢光強弱變化的差異。此新型螢光複合材料可應用於偵測細菌。

關鍵字

原子轉移自由基聚合 ； 奈米矽片 ； 聚異丙基丙烯醯胺 ； 臨界微胞濃度 ； 奈米銀粒子 ； 最低臨界溶解溫度 ； 聚六乙基甲基丙烯酸酯 ； 物理捕捉效應 ； 螢光偵測

並列摘要

Nanoscale silicate platelets (NSP) were derived from the exfoliation of naturally occurring sodium montmorillonite clay. The silicate platelets were modified with two different polymers via a novel initiator covalently bonded to the edge of NSP by a sol–gel reaction and atom transfer radical polymerization (ATRP) to afford the new class of nanohybrids. In this study, we grafted poly(N-isopropylacrylamide) (PNiPAAm) onto the edge of NSP through the covalent bonding with single- or double-headed linkers to prepare the NSP-PNiPAAm nanohybrids. By tailoring the architecture of the linker and controlling the number of grafted linkers, we were able to prepare NSP-PNiPAAm of varios grafting densities. The inherent ionic character of NSP and the organic moieties of isopropyl amide in PNiPAAm impart surfactant-like properties to the nanohybrids. Surface tension and particle size measurements were used to determine the critical micelle concentration (CMC) of the nanohybrids. The CMC can be tailored by adjusting the densities and architectures of the linkers. The NSP-PNiPAAm nanohybrids from single-headed linkers are loosely packed and can easily expand in water to faciliate inter-hybrid interactions to render a low CMC. In contrast, the nanohybrids from double-headed linkers enhance intra-hybrid interactions, thus exhibiting a higher CMC. The simulation results were found to be in a good agreement with the experimental observations.
We further introduced silver nanoparticles (AgNPs) onto NSP-PNiPAAm. The generated AgNPs had an average diameter of 8 nm with a narrow size distribution. The AgNP/NSP-PNiPAAm exhibited the property of lowest critical solution temperature (LCST) at 32 oC, which was similar to the LCST of the NSP-PNiPAAm precursor. This is a clear indication of AgNPs attachment on the NSP surface rather than with PNiPAAm organic chains. The strong embedment between AgNPs and NSP was evidenced by transmission electron microscopic (TEM) and LCST thermal cycles between 28-37 oC monitored by ultraviolet-visible spectrophotometry (UV-vis). At 37 oC, the nanohybrids and E. coli give stronger SERS intensities and hydrophobic interaction than the hydrophilic B. subtilis counterparts. In contrast at 28 oC, the nanohybrids interact with hydrophilic B. subtilis, thus giving a relatively strong SERS intensities. Similar results were also observed in their antibacterial ability. It could be thus anticipated that the new AgNP/NSP-PNiPAAm hybrids have good potentials to serve as biosensors and antibacterial materials.
We have also synthesized new fluorescent nanohybrids via tethering poly(hydroxyethyl methacrylate) pendants (HEMA) onto NSP through a sol-gel and living polymerization and by a further modification of the pendants with a nathphalimide-type fluorescence compound. The fluorescent NSP-PHEMA-HA was characterized for their photoluminescence (PL) and bacterial trapping properties from NSP’s affinity toward the surface of bacteria. In addition, the investigation of PL emission revealed that the fluorescent NSP hybrids could be applicable in bacteria detection. The fluorescent NSP hybrids are proposed for the biosensor applications for the combined features of photoluminescence and physical trapping for bacteria.

並列關鍵字

atom transfer radical polymerization ； nano silicate platelets ； poly(N-isopropylacrylamide) ； critical micelle concentrations ； silver nanoparticles ； lowest critical solution temperature ； poly(hydroxyethyl methacrylate) ； physical trapping ； fluorescent sensors

參考文獻

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