AI 中文总结
该研究揭示了P(NIPAM-co-NIPMAM)微凝胶的类嵌段单体分布及内部异质性随NIPMAM含量的变化规律，为定制功能软材料的响应性胶体提供了设计准则。
AI 中文摘要
理解共聚物微凝胶的内部结构对于建立纳米级聚合物组织如何控制其刺激响应行为至关重要。本研究聚焦于通过自由基沉淀聚合合成的、组分摩尔分数不同的热响应聚（N-异丙基丙烯酰胺-co-N-异丙基甲基丙烯酰胺），即P(NIPAM-co-NIPMAM)微凝胶，证明其体积相转变和平衡溶胀的变化由与组成相关的内部异质性所调控。结合同位素标记的小角中子散射（SANS）与单体分辨模拟的对比显示，两种组分呈类嵌段的单体分布。SANS分析揭示，聚合物网格的相关长度在相转变附近存在一个普适最大值，证实富NIPAM的塌缩区域与溶胀区域共存。相关长度随NIPMAM含量的增加而增大，在NIPMAM摩尔分数为75%时达到最大值，这意味着网络内的塌缩区域较为稀疏，且因存在比例不断增大的嵌入型非塌缩PNIPMAM组分，引发了高度异质性。最大异质性与平衡溶胀比相关，表明塌缩的微凝胶保留了相转变的结构记忆，对温度变化呈现出更不易变形的结构。总体而言，这些见解凸显了类嵌段单体分布对不同组成共聚物微凝胶响应特性的复杂影响，为定制功能软材料的响应性胶体提供了设计准则。
英文摘要
Understanding the internal architecture of copolymer microgels is crucial for establishing how nanoscale polymer organization controls their stimuli-responsive behavior. Here we focus on thermoresponsive P(N-isopropylacrylamide-co-N-isopropyl-methacrylamide), P(NIPAM-co-NIPMAM), microgels with varying mole fraction of the components, synthesized via radical precipitation polymerization, and we demonstrate that changes in their volume phase transition and equilibrium swelling are governed by composition-dependent internal heterogeneity. Comparison between small-angle neutron scattering (SANS) with isotopic labeling and monomer-resolved simulations show a block-like monomer distribution of the two components. SANS analysis reveals a universal maximum in the polymer mesh correlation length near the transition, evidencing coexistence of collapsed NIPAM-rich and swollen domains. The correlation length increases with increasing NIPMAM content, with a maximum for 75 mol \% NIPMAM, implying sparse collapsed regions within the network and thus a large degree of heterogeneity induced by the presence of an increasingly large fraction of intercalated, non-collapsing PNIPMAM. The maximum heterogeneity correlates with the equilibrium swelling ratio, indicating that collapsed microgels retain a structural memory of the transition and present a less-compliant structure in response to temperature variations. Overall, these insights highlight a complex effect of the block-like monomer distribution on the responsive properties of copolymer microgels with different compositions, thus providing a design rule for tailoring responsive colloids for functional soft materials.
