Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, 08544, USA.
Department of Chemistry, Key Laboratory of Advanced Textile Materials and Manufacturing Technology of the Education Ministry, Zhejiang Sci-Tech University, Hangzhou, 310018, China.
Macromol Rapid Commun. 2020 Mar;41(6):e1900582. doi: 10.1002/marc.201900582. Epub 2020 Feb 9.
Annealing a supported polymer film in the melt state results in the growth of an irreversibly adsorbed layer, which has been shown to influence thin film properties such as diffusion and glass transition temperature. Adsorbed layer growth is attributed to many simultaneous interactions between individual monomer units and the substrate, stabilizing chains against desorption. In this study, adsorbed layers of polystyrene (PS), poly(methyl methacrylate) (PMMA), and their random copolymers are isolated by select solvents. While PS adsorbed layer thickness is largely unaffected by the choice of washing solvent, the PMMA adsorbed layer completely desorbs when washed with tetrahydrofuran and chloroform, as opposed to toluene. Scaling relationships between adsorbed layer thickness and degree of chain adsorption at the substrate enable the use of adsorbed layer thickness to probe specific polymer-substrate interactions. Composition-dependent desorption trends indicate non-preferential adsorption between styrene and methyl methacrylate repeat units at the substrate, despite differences in substrate interaction strength. This insight contributes to the developing mechanism for the adsorption of random copolymers during melt-state annealing, further extending the ability to predict processing-inducted changes to the properties of polymer thin films to heterogeneous systems.
在熔融状态下退火支撑的聚合物膜会导致不可逆吸附层的生长，这已被证明会影响薄膜的扩散和玻璃化转变温度等特性。吸附层的生长归因于单体单元与基底之间的许多同时相互作用，这些相互作用稳定了链，防止它们解吸。在这项研究中，通过选择溶剂将聚苯乙烯（PS）、聚甲基丙烯酸甲酯（PMMA）及其无规共聚物的吸附层分离。虽然 PS 吸附层厚度受洗涤溶剂选择的影响不大，但 PMMA 吸附层在用四氢呋喃和氯仿洗涤时会完全解吸，而不是甲苯。吸附层厚度与链在基底上吸附程度之间的标度关系使得可以使用吸附层厚度来探测特定的聚合物-基底相互作用。组成依赖性的解吸趋势表明，尽管基底相互作用强度存在差异，但苯乙烯和甲基丙烯酸甲酯重复单元在基底上的吸附是非优先的。这一见解有助于发展熔融态退火过程中无规共聚物吸附的机制，进一步扩展了预测聚合物薄膜性质在加工诱导变化的能力，使其能够应用于非均相体系。
