Self-organization-induced three-dimensional honeycomb pattern in structure-controlled bulky methacrylate polymers: Synthesis, morphology, and mechanism of pore formation
Self-organization-induced three-dimensional honeycomb pattern in structure-controlled bulky methacrylate polymers: Synthesis, morphology, and mechanism of pore formation
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DOI：
10.1021/jp063469a
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发表时间：
2006-11-02
影响因子：
3.3
通讯作者：
Asha, S. K.
中科院分区：
文献类型：
--
作者：
Deepak, V. D.;Asha, S. K.
在这里，我们首次报道了一种新的分子设计，通过在甲基丙烯酸聚合物主链中自组织氢键大体积锚定基团来实现三维蜂窝结构。可聚合单体设计包括一个甲基丙烯酸双键，通过氢键环脂肪族脲烷连接到各种疏水锚定单元，如乙烷、正癸烷、三环癸烷（TCD）和adamantane。用核磁共振（NMR）证实了聚合物的结构，并用凝胶渗透色谱（GPC）测定了聚合物的分子量。具有三环癸烷和adamantane庞大锚定基团的甲基丙烯酸酯聚合物在环境条件下在四氢呋喃-水溶剂混合物中自组织产生三维蜂窝图案，而其线性类似物（乙烷，正癸烷）不能产生任何微图案。对制备的聚合物薄膜进行扫描电镜（SEM）分析表明，聚合物的结构对蜂窝图案的形成起主要作用。溶液傅里叶变换红外（FTIR）测量证实，与线性类似物相比，体积较大的三环癸烷和金刚烷聚合物具有较强的氢键相互作用，这是微图案的驱动力。透射电子显微镜（TEM）和原子力显微镜（AFM）分析表明，聚合物在溶液中以囊泡或胶束的形式存在，从而形成蜂窝状图案。大体积聚合物体系中蜂窝状结构的形成表明，氢键相互作用和大体积锚定单元的疏水性是诱导三维蜂窝结构的两个协同因素。采用过氧化苯甲酰（BPO）引发自由基和原子转移自由基聚合（ATRP）技术进行聚合，研究了分子量及其分布对自组织过程的影响。微孔的形成与分子量和多分散指数（PDI）的差异无关；孔径分布受分子量和PDI的共同影响。低分子量样品提供了多分散的孔隙，而ATRP样品的PDI更窄，产生了大尺寸的孔隙。该方法也被用于聚苯乙烯-大块甲基丙烯酸共聚物的研究，结果表明，当大块单元的掺入量超过50 mol %时，共聚物可以产生均匀的蜂窝图案。
Here we report, for the first time, a novel molecular design for three-dimensional honeycomb structures through a self-organization of hydrogen-bonded bulky anchoring group in a methacrylic polymer backbone. The polymerizable monomer design includes a methacrylic double bond linked to various hydrophobic anchoring units such as ethane, n-decane, tricyclodecane (TCD), and adamantane via a hydrogen-bonded cycloaliphatic urethane linkage. The structures of the polymers were confirmed by nuclear magnetic resonance (NMR) and the molecular weights of the polymer were determined by gel permeation chromatography (GPC). The methacrylate polymers having tricyclodecane and adamantane bulky anchoring groups self-organized to produce three-dimensional honeycomb patterns in tetrahydrofuran-water solvent mixture at ambient conditions, whereas its linear analogues (ethane, n-decane) failed to produce any micropattern. The scanning electron microscopy (SEM) analysis of the above-prepared polymer films revealed that the structure of the polymer played a major role in the formation of the honeycomb patterns. The solution Fourier transform infrared (FTIR) measurements confirmed that the bulky tricyclodecane and adamantane polymers have strong hydrogen-bonding interaction compared to that of their linear analogues, which is the driving force for the micropatterns. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) analysis of the bulky polymers revealed that the polymers exist as vesicles or micelles in the solution, which leads to the formation of the honeycomb pattern. The honeycomb pattern formation in the bulky polymer systems suggests that two cooperative factors such as hydrogen- bonding interaction and hydrophobicity of bulky anchoring units are necessary to induce three-dimensional honeycomb structures. To investigate the effect of molecular weights and its distribution on the self-organization process, both benzoyl peroxide (BPO) initiated free radical and atom transfer radical polymerization (ATRP) techniques were employed for the polymerization. Micropores formed irrespective of differences in molecular weight and polydispersity index (PDI); however, the pore size distribution was influenced by both molecular weights and PDI. Low molecular weight samples afforded polydisperse pores with the ATRP samples with more narrow PDI producing pores with large dimensions. The approach has also been investigated for polystyrene-bulky methacrylic copolymer, and the results revealed that uniform honeycomb patterns were produced for copolymers having more than 50 mol % incorporation of bulky units.