(312c) Modeling and Control of Copolymer Sequence Length and Distribution for Controlled Radical Polymerization in a Semi-Batch Reactor

Controlled/living radical polymerization (CRP) has received great attention over the past years. The advent of CRP techniques including atom-transfer free-radical polymerization (ATRP), reversible addition-fragmentation chain transfer polymerization (RAFT), and nitroxide-mediated radical polymerization (NMRP) has greatly renewed interests in radical polymerization because CRP allows us to achieve a high degree of control over polymeric molecular architecture under relatively mild conditions. It is well known that copolymer composition has a significant effect on the properties of a resulting copolymer. Thus, it is important to control copolymer composition in CRP to obtain desired properties. The design and control of copolymer composition for RAFT copolymerization system is being done through an optimized semi-batch operation. Other than copolymer composition, it is believed that the sequence length and distribution also practically affect copolymer properties such as copolymer interfacial activity, hydrogen bonding strength, and crystallinity. However, the modeling and control of sequence length and distribution receive little attention. In this work, we developed a sequence model using moment equations to describe sequence length and distribution in semi-batch operations for a CRP system such as a RAFT system, or a NMRP system, etc. With the sequence model, we are able to not only calculate the sequence length and distribution while controlling constant composition and linear gradient composition, but also control more detailed molecular architecture, the sequence length. With the aid of a sequence model, it can be utilized as a useful theoretical tool to design and control the sequence length and distribution for a CRP system.