RAFT polymerization of styrene mediated by oxazolyl-functionalized trithiocarbonate RAFT agents

• Published in: Polymer bulletin (Berlin, Germany) Germany), 2021-04, Vol.78 (4), p.2251-2285
• Main Authors: Summers, Gabriel J., Motsoeneng, Teboho S., Summers, Carol A.
• Format: Article
• Language: English
• Subjects: Acids; Addition polymerization; Chain transfer; Chains (polymeric); Characterization and Evaluation of Materials; Chemical reactions; Chemistry; Chemistry and Materials Science; Chloride; Chromatography; Complex Fluids and Microfluidics; Consumption; Drug therapy; Fourier transforms; Fragmentation; Hydrochloric acid; Initiation (polymerization); Initiators; Mass spectrometry; Molecular weight; Molecular weight distribution; Monomers; Organic Chemistry; Original Paper; Physical Chemistry; Polymer Sciences; Polymerization; Polymers; Polystyrene resins; Radicals; Scientific imaging; Sodium; Soft and Granular Matter; Solvents; Styrenes
• ISSN: 0170-0839; 1436-2449
• DOI: 10.1007/s00289-020-03211-6

New oxazolyl benzhydryl and oxazolyl benzyl-functionalized trithiocarbonate RAFT agents, 1-(butylsulfanylthiocarbonylsulfanyl)-1-[4-(4,5-dihydro-4,4-dimethyl-2-oxazolyl)phenyl]-1-phenylmethane and 2-[4-((butylsulfanylthiocarbonylsulfanyl)methyl)phenyl]-4,5-dihydro-4,4-dimethyloxazole, were prepared and employed as chain transfer agents in RAFT polymerization reactions. The RAFT polymerization of styrene, mediated by the appropriate oxazolyl-functionalized trithiocarbonate RAFT agent with AIBN as initiator at 70 °C, proceeded via controlled/living polymerization processes to produce the corresponding α-oxazolyl-functionalized polystyrene derivative, with the oxazolyl group introduced at the α-terminus of the polymer chain and the absence of any unfunctionalized polystyrene. Post-RAFT polymerization chain end modification of α-oxazolyl-functionalized polystyrene by acid-catalyzed hydrolysis reactions with dilute hydrochloric acid afforded the corresponding α-carboxyl-functionalized polystyrene derivative, with the retention of the butylsulfanylthiocarbonylsulfanyl moiety at the ω-terminus of the polymer chain. Polymer kinetic measurements show that each RAFT polymerization reaction follows first-order rate kinetics with respect to the percentage monomer consumption. The oxazolyl-functionalized benzhydryl fragmentation radical provides better control of the re-initiation of the polymerization of styrene than the oxazolyl-functionalized benzyl fragmentation radical. After consumption of the RAFT agent, the number average molecular weights of the functionalized polymers increases linearly with the percentage monomer conversion to produce α-oxazolyl-functionalized polystyrene derivatives with narrow molecular weight distributions. Graphic abstract New oxazolyl benzhydryl and oxazolyl benzyl-functionalized trithiocarbonate RAFT agents, 1-(butylsulfanylthiocarbonylsulfanyl)-1-[4-(4,5-dihydro-4,4-dimethyl-2-oxazolyl)phenyl]-1-phenylmethane and 2-[4-((butylsulfanylthiocarbonylsulfanyl)methyl)phenyl]-4,5-dihydro-4,4-dimethyloxazole, were prepared and employed as chain transfer agents in RAFT polymerization reactions. The RAFT polymerization of styrene, mediated by 1-(butylsulfanylthiocarbonylsulfanyl)-1-[4-(4,5-dihydro-4,4-dimethyl-2-oxazolyl)phenyl]-1-phenylmethane or 2-[4-((butylsulfanylthiocarbonylsulfanyl)methyl)phenyl]-4,5-dihydro-4,4-dimethyloxazole as chain transfer agents with AIBN as the initiator at 70 °C, proceeds via a controlled/living polymerization pro