Taehyoung Kim, En Wang, Joanna M. White, Frank S. Bates, Timothy P. Lodge
{"title":"通过时间分辨小角中子散射研究不对称 ABA′三嵌段聚合物胶束中的链交换动力学","authors":"Taehyoung Kim, En Wang, Joanna M. White, Frank S. Bates, Timothy P. Lodge","doi":"10.1021/acs.macromol.4c01687","DOIUrl":null,"url":null,"abstract":"The effect of corona block asymmetry on chain exchange kinetics has been investigated using time-resolved small-angle neutron scattering (TR-SANS) with a series of AB di- and ABA′ triblock micelles composed of poly(ethylene-<i>alt</i>-propylene) (A) and polystyrene (B) block copolymers in squalane. The four copolymers maintain constant molecular weight and total block composition, but have different asymmetry ratios of the end blocks, denoted as SEP, EPSEP′-1, EPSEP′-2, and EPSEP. The TR-SANS results reveal a 10-fold acceleration in the chain exchange rate for asymmetric triblock copolymer micelles (EPSEP′-1 and EPSEP′-2) and a hundred-fold acceleration for symmetric triblock copolymers (EPSEP), compared to the SEP diblock copolymer. This enhanced exchange rate is primarily attributed to differences in the micelle structure associated with corona chain entropy during extraction, supported by calculations of grafting chain density and stretching of corona chains. Thus, this study demonstrates an interesting and significant role of block copolymer asymmetry in molecular exchange dynamics.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"30 1","pages":""},"PeriodicalIF":5.1000,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Kinetics of Chain Exchange in Asymmetric ABA′ Triblock Polymer Micelles by Time-Resolved Small-Angle Neutron Scattering\",\"authors\":\"Taehyoung Kim, En Wang, Joanna M. White, Frank S. Bates, Timothy P. Lodge\",\"doi\":\"10.1021/acs.macromol.4c01687\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"The effect of corona block asymmetry on chain exchange kinetics has been investigated using time-resolved small-angle neutron scattering (TR-SANS) with a series of AB di- and ABA′ triblock micelles composed of poly(ethylene-<i>alt</i>-propylene) (A) and polystyrene (B) block copolymers in squalane. The four copolymers maintain constant molecular weight and total block composition, but have different asymmetry ratios of the end blocks, denoted as SEP, EPSEP′-1, EPSEP′-2, and EPSEP. The TR-SANS results reveal a 10-fold acceleration in the chain exchange rate for asymmetric triblock copolymer micelles (EPSEP′-1 and EPSEP′-2) and a hundred-fold acceleration for symmetric triblock copolymers (EPSEP), compared to the SEP diblock copolymer. This enhanced exchange rate is primarily attributed to differences in the micelle structure associated with corona chain entropy during extraction, supported by calculations of grafting chain density and stretching of corona chains. Thus, this study demonstrates an interesting and significant role of block copolymer asymmetry in molecular exchange dynamics.\",\"PeriodicalId\":51,\"journal\":{\"name\":\"Macromolecules\",\"volume\":\"30 1\",\"pages\":\"\"},\"PeriodicalIF\":5.1000,\"publicationDate\":\"2024-10-23\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Macromolecules\",\"FirstCategoryId\":\"92\",\"ListUrlMain\":\"https://doi.org/10.1021/acs.macromol.4c01687\",\"RegionNum\":1,\"RegionCategory\":\"化学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"POLYMER SCIENCE\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Macromolecules","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1021/acs.macromol.4c01687","RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"POLYMER SCIENCE","Score":null,"Total":0}
Kinetics of Chain Exchange in Asymmetric ABA′ Triblock Polymer Micelles by Time-Resolved Small-Angle Neutron Scattering
The effect of corona block asymmetry on chain exchange kinetics has been investigated using time-resolved small-angle neutron scattering (TR-SANS) with a series of AB di- and ABA′ triblock micelles composed of poly(ethylene-alt-propylene) (A) and polystyrene (B) block copolymers in squalane. The four copolymers maintain constant molecular weight and total block composition, but have different asymmetry ratios of the end blocks, denoted as SEP, EPSEP′-1, EPSEP′-2, and EPSEP. The TR-SANS results reveal a 10-fold acceleration in the chain exchange rate for asymmetric triblock copolymer micelles (EPSEP′-1 and EPSEP′-2) and a hundred-fold acceleration for symmetric triblock copolymers (EPSEP), compared to the SEP diblock copolymer. This enhanced exchange rate is primarily attributed to differences in the micelle structure associated with corona chain entropy during extraction, supported by calculations of grafting chain density and stretching of corona chains. Thus, this study demonstrates an interesting and significant role of block copolymer asymmetry in molecular exchange dynamics.
期刊介绍：
Macromolecules publishes original, fundamental, and impactful research on all aspects of polymer science. Topics of interest include synthesis (e.g., controlled polymerizations, polymerization catalysis, post polymerization modification, new monomer structures and polymer architectures, and polymerization mechanisms/kinetics analysis); phase behavior, thermodynamics, dynamic, and ordering/disordering phenomena (e.g., self-assembly, gelation, crystallization, solution/melt/solid-state characteristics); structure and properties (e.g., mechanical and rheological properties, surface/interfacial characteristics, electronic and transport properties); new state of the art characterization (e.g., spectroscopy, scattering, microscopy, rheology), simulation (e.g., Monte Carlo, molecular dynamics, multi-scale/coarse-grained modeling), and theoretical methods. Renewable/sustainable polymers, polymer networks, responsive polymers, electro-, magneto- and opto-active macromolecules, inorganic polymers, charge-transporting polymers (ion-containing, semiconducting, and conducting), nanostructured polymers, and polymer composites are also of interest. Typical papers published in Macromolecules showcase important and innovative concepts, experimental methods/observations, and theoretical/computational approaches that demonstrate a fundamental advance in the understanding of polymers.
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