Asymmetric copolymers: Neither block nor random

• Applicant: Carlos Antioco Guerrero Sanchez, Ph.D.
• Subject Area: Polymer Materials
• Term: from 2015 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 286983008

The goal of the ASYMCOPO project is to develop new materials that mimic the useful properties of gradient copolymers, but which do not require complex synthetic procedures for their preparation. 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 noise-absorbers and as interfacial stabilizers. However, the preparation of a polymer with a pre-defined gradient of composition requires a semi-continuous process with careful control over monomer addition and constant feedback in order to regulate the composition at each stage of the polymerization. It has recently been noted that the very idea of a gradient copolymer is something of a contradiction in terms: while the average composition of all the chains of a polymer may vary smoothly from one end of the chain to the other, each individual chain is composed of discrete monomer units, and at any point in the chain the composition must take one of only two possible values. Thus, polymers which, on average, exhibit a composition gradient contain a broad distribution of structures. Furthermore, it is impossible to reconstruct the composition gradient of the entire polymer from a single polymer chain. It is thus natural to ask, what is the defining structural feature of a gradient copolymer? And can these properties be mimicked using structures that are easier to prepare, using well-understood batch polymerization processes? In the ASYMCOPO project we aim to answer this question by introducing the concept of asymmetric copolymers: polymers that are intermediate in structure between block and random copolymers. We have developed a framework for the classification of this class of polymers, centered on the concept of a moment of asymmetry, which we will use to guide our research in first synthesizing, then exploring the properties of this new class of materials. In particular, we seek to define structures consisting of 2, 3, or 4 random copolymer segments which mimic the useful properties of gradient copolymers, but are substantially easier to synthesize. This project requires the preparation of an extensive library of copolymers of different structures, and hence necessitates the involvement of a laboratory with expertise in high-throughput polymer synthesis and characterization. The Institute for Organic and Macromolecular Chemistry (IOMC), in Jena, Germany, is the European leading research group in this domain. In parallel, synthesis of well-defined gradient copolymers requires careful control of polymerization conditions, employing the expertise of the Laboratoire des Intéractions Moléculaires et Réactivité Chimique et Photochimique (IMRCP) laboratory of Toulouse, France, in polymerization kinetics, polymer synthesis and characterization.

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partner: Simon Harrisson, Ph.D.