Interplay between hydrogen bonding and macromolecular architecture leading to unusual phase behavior in thermosensitive microgels.
Interplay between hydrogen bonding and macromolecular architecture leading to unusual phase behavior in thermosensitive microgels.
复制标题
DOI：
10.1002/anie.200703728
复制
发表时间：
2008
影响因子：
--
通讯作者：
Martina Keerl;V. Smirnovas;R. Winter;W. Richtering
中科院分区：
文献类型：
--
作者：
Martina Keerl;V. Smirnovas;R. Winter;W. Richtering
蛋白质的折叠过程通常是由链内和链间氢键、疏水和静电相互作用引起的，并导致相当复杂的生物活性结构。一些合成聚合物可以显示类似于蛋白质的大分子结构，因此可以作为更简单但合适的模型系统来研究折叠过程的特定特征。[1]聚-N-异丙基丙烯酰胺（PNIPAM）在328 ℃发生可逆转变，这归因于分子内和分子间氢键的形成。线性PNIPAM的线团到小球的转变已经通过量热法，[2]荧光光谱，[3]光散射，[4]和红外光谱进行了研究。[5]计算机模拟表明，折叠过程的强烈影响的聚合物结构。[6]合成聚合物体系的结构可以通过化学交联、共聚或形成核-壳结构来改性。后者导致可调的相变温度和变量间和不同的隔间之间的分子内相互作用。不同的核-壳微凝胶系统最近由不同的研究小组报道。特别是，具有热敏性核和刺激响应性壳的核-壳系统显示出独特的性质。[7]温敏聚合物从线团到小球的相变是由于疏水作用和氢键之间的微妙平衡。核-壳系统由具有特定相互作用的不同区域组成;一方面，核和壳具有各自的温敏疏水相互作用，另一方面，核/壳界面，其中核和壳材料直接连接，这导致核和壳溶胀的相互影响。[8]最近，我们报道了由N-异丙基丙烯酰胺（NIPAM）和N，N-二乙基丙烯酰胺（DEAAM）组成的热敏交联共聚物微凝胶，其揭示了取决于组合物的相变温度的不寻常的抑郁症。[9]体积相转变温度（VPTT）对于1：1共聚物具有最小值，即转变温度低于相应的均聚物颗粒的转变温度。这种不寻常的协同行为可能是由共聚物微凝胶中单取代和双取代丙烯酰胺重复单元之间的强氢键引起的。在这项工作中，我们endeeless调查的氢键模式的微凝胶组成的NIPAM和DEAAM的傅里叶变换红外光谱（FTIR），这已被证明是一个有用的工具，探测分子内和分子间的氢键。[10]所述共聚物和
Generally, folding processes of proteins are caused by intraand interchain hydrogen bonding, as well as hydrophobic and electrostatic interactions, and lead to rather complex bioactive structures. Some synthetic polymers can display macromolecular structures similar to proteins and thus may serve as simpler, though appropriate, model systems to study particular features of folding processes. [1] Poly-N-isopropylacrylamide (PNIPAM) undergoes a reversible transition at 328C attributed to the formation of intra- and intermolecular hydrogen bonds. The coil-to-globule transition of linear PNIPAM has been investigated by calorimetry, [2] fluorescence spectroscopy, [3] light scattering, [4] and infrared spectroscopy. [5] Computer simulations show that the folding process is strongly influenced by the polymer structure. [6] The architecture of a synthetic polymer system can be modified by chemical cross-linking, copolymerization, or the formation of core–shell architectures. The latter leads to tunable phase transition temperatures and to variable inter- and intramolecular interactions between the different compartments. Different core–shell microgel systems were reported recently by separate research groups. In particular, core– shell systems with a thermosensitive core and a stimuliresponsive shell show unique properties. [7] The coil-to-globule phase transition of thermosensitive polymers is attributed to a delicate balance between hydrophobic interaction and hydrogen bonding. A core–shell system is composed of different regions with specific interactions; on the one hand, the core and shell with their individual thermoresponsive hydrophobic interactions and on the other hand, the core/shell interface where the core and shell materials are directly connected, which leads to a mutual influence of core and shell swelling. [8] Recently, we reported thermosensitive cross-linked copolymer microgels consisting of N-isopropylacrylamide (NIPAM) and N,N-diethylacrylamide (DEAAM) that reveal an unusual depression of the phase transition temperature depending on the composition. [9] The volume phase transition temperature (VPTT) has a minimum for the 1:1 copolymer, that is, the transition temperature is lower than that of the corresponding homopolymer particles. This unusual, synergistic behavior could be caused by strong hydrogen bonding between the mono- and disubstituted acrylamide repeating units in the copolymer microgel. In this work we endeavored to investigate the hydrogenbonding pattern of microgels consisting of NIPAM and DEAAM by Fourier-transform infrared (FTIR) spectroscopy, which has proved to be a useful tool to probe intra- and intermolecular hydrogen bonding. [10] The copolymer and