Thermally induced gelation of poly(acrylamide) grafted with poly(N-isopropylacrylamide):: A small-angle neutron scattering study
Thermally induced gelation of poly(acrylamide) grafted with poly(N-isopropylacrylamide):: A small-angle neutron scattering study
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DOI：
10.1021/ma049182y
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发表时间：
2004-07-27
期刊：
影响因子：
5.5
通讯作者：
Viovy, JL
中科院分区：
文献类型：
--
作者：
Barbier, V;Hervé, M;Viovy, JL
在毛细管电泳DNA测序的框架下，建立了聚n -异丙基丙烯酰胺（PNIPAM）接枝聚丙烯酰胺的筛分基质。由于其热力学性质，PNIPAM侧链在临界温度以上自聚集，导致在半稀溶液中产生强烈的热增稠效应。我们在此报告了一项在D(2)O中进行的瞬态网络形成研究，该研究基于大量具有不同尺寸（M(w) = 10,000, 20,000和35,000 g/mol）和不同接枝密度（5,7,10,14和18% w/w）的PNIPAM接枝的响应共聚物。对于大多数水溶液，当温度高于某一临界值时，在有限散射矢量处观察到一个相关峰。散射峰强度随PNIPAM贴片尺寸、接枝密度、浓度和温度的增加而增大。实验数据使用核-电晕模型拟合，假设只有部分PNIPAM接枝（f(PNIPAM)，质量分数）参与聚集过程（干胶束）。在这些假设下，根据共聚物的主要结构，五参数模型可以真实地描述热诱导关联，核心尺寸范围在70到100 a之间，而PNIPAM （PNIPAM）的变化范围在18%到50%之间。基质之间的比较证实，基于响应性聚集的物理网络是DNA测序的良好候选者，即使它们显示出拮抗特性，这是由于(1)由于基质凝胶化（特别是对于大的DNA片段）而增加的分辨率，以及(2)由于疏水结构域和DNA之间的特定相互作用而导致分离过程中DNA片段的分散，从而导致分辨率的损失。
Sieving matrixes of poly(acrylamide) grafted with poly(N-isopropylacrylamide) (PNIPAM) were developed in the framework of DNA sequencing by capillary electrophoresis. As a result of their thermodynamic properties, PNIPAM side chains self-aggregate above a critical temperature, leading to strong thermo-thickening effects in semidilute solutions. We report here a study of the transient network formation, carried out in D(2)O by small-angle neutron scattering on the basis of a large set of responsive copolymers tailored with PNIPAM grafts of different sizes (M(w) = 10 000, 20 000, and 35 000 g/mol) and various graft densities (5, 7, 10, 14, and 18% w/w). For most of the aqueous solutions, a correlation peak is observed at finite scattering vectors when the temperature is increased above a critical value. The intensity of the scattering peak rises with the size of the PNIPAM stickers, the graft density, the concentration, and the temperature. Experimental data are fitted using a core-corona model, assuming that only part of PNIPAM grafts (f(PNIPAM), mass fraction) participate in the aggregation process (dry micelles). Under these assumptions, the five-parameter model allows a realistic description of the thermally induced association with core sizes ranging between 70 and 100 A and f(PNIPAM) varying between 18 and 50%, depending on the primary structure of the copolymers. Comparison between matrixes confirms that physical networks based on responsive aggregation are good candidates for DNA sequencing even if they display antagonistic properties arising from (1) an increase of the resolution due to the matrix gelation (especially for large DNA fragments) and (2) a dispersion of DNA fragments during separation due to specific interactions between hydrophobic domains and DNA, which results in a loss of resolution.