Asymmetric copolymers: Neither block nor random
Final Report Abstract
Gradient copolymers, whose composition varies continuously as a function of chain length, are an intriguing class of materials with many potential applications, including as shock- and noiseabsorbers and as interfacial stabilizers. However, the preparation of a polymer with a predefined gradient of composition requires complex synthetic procedures, for example, a semicontinuous process with careful control over monomer addition and constant feedback in order to regulate the composition at each stage of the polymerization. In the ASYMCOPO project we aimed to prepare simple analogs of gradient copolymers that we call ‘asymmetric copolymers’: polymers that are intermediate in structure between block and random copolymers. Thus, this approach was investigated using copolymers with very simple structures, e.g. diblock and triblock, which can be synthesized through a substantially easier approach via one-pot polymerization to mimic the properties of gradient copolymers. The resulting polymers showed numerous similarities to gradient copolymers, including broad glass transitions, and the formation of dynamic self-assembled aggregates in solution. These polymers could undergo different types of morphological transitions, from micelles to wormlike micelles to vesicles, induced by the pH of their aqueous solution. The self-assemblies of diblock, triblock, and gradient copolymers displayed dynamic and controlled release of Nile Red in responding to environmental pH whereas Nile Red stayed encapsulated in the “frozen” micelles of the block copolymers. In addition, we developed a framework for the classification of this class of polymers, centered on the concept of a ‘moment of asymmetry,’ which used to guide our research in first synthesizing, then exploring the properties of this new class of materials. In particular, we sought to define block copolymer structures consisting of 2 or 3 random copolymer segments which mimic the useful properties of gradient copolymers, but are substantially easier to synthesize. These new materials should help us to understand the relationship between monomer distribution and copolymer properties, and define the essential characteristics of a gradient copolymer. The methodology developed in this project provides a new perspective for the synthesis of gradient-like copolymers utilizing much simplifier experimental setup and process. This approach can be applied to other monomer systems to synthesize polymeric materials with properties that can be adjusted at will and with useful applications in real life.
Publications
- Thermosensitive spontaneous gradient copolymers with block-and gradient-like features. Polym. Chem. 2017, 8, 5023-5032
R. Yañez-Macias, I. Kulai, J. Ulbrich, T. Yildirim, P. Sungur, S. Hoeppener, R. Guerrero-Santos, U. S. Schubert, M. Destarac, C. Guerrero-Sanchez, S. Harrisson
(See online at https://doi.org/10.1039/c7py00495h) - Asymmetric copolymers: Synthesis, properties, and applications of gradient and other partially segregated copolymers, Macromol. Rapid Commun. 2018, 39, 1800357
J. Zhang, B. Farias‐Mancilla, M. Destarac, U. S. Schubert, D. J. Keddie, C. Guerrero‐Sanchez, S. Harrisson
(See online at https://doi.org/10.1002/marc.201800357) - High throughput synthesis of polymers, in Encyclopedia of Polymer Science and Technology, John Wiley & Sons, 2018
C. Guerrero‐Sanchez, J. Zhang, J. Vitz, U. S. Schubert
(See online at https://doi.org/10.1002/0471440264.pst668) - Kinetic and copolymer composition investigations of the free radical copolymerization of 1-octene with glycidyl methacrylate, Macromol. Chem. Phys. 2018, 219, 1800084
M. Rosales-Guzmán, O. Pérez-Camacho, R. Torres-Lubián, S. Harrisson, U. S. Schubert, C. Guerrero-Sánchez, E. Saldívar-Guerra
(See online at https://doi.org/10.1002/macp.201800084) - Enzyme degassing for oxygen-sensitive reactions in open vessels of an automated parallel synthesizer: RAFT polymerizations, ACS Comb. Sci. 2019, 21, 643−649
M. Wang, J. Zhang, C. Guerrero-Sanchez, U. S. Schubert, A. Feng, S. H. Thang
(See online at https://doi.org/10.1021/acscombsci.9b00082)
