Synthesis of High Molecular Weight Polymers by Organocatalyzed Living Radical Polymerization and Self-Assembly Behavior

A mild organocatalyzed living radical polymerization method is studied for high molecular weight polymers (HMWPs), yielding low-dispersity linear and star polymers (D = M-w/M-n = 1.03-1.28) up to M-n = 3.9 x 10(5) and monomer conversion = 80%, where M-n and M-w are the number- and weight-average molecular weights, respectively. Even at high degrees of polymerization (DPs > 2000), this technique still features excellent control over molecular weights and D values, indicating the living character. The macroinitiators prepared at DP = 2000 are subsequently used for block polymerizations at high DPs (>2000) with functional methacrylates, yielding linear A-B diblock, linear B-A-B triblock, and 3-arm star A-B diblock copolymers, suggesting the excellent block efficiency of macroinitiators synthesized at a high DP value (=2000). This mild organocatalyzed living radical polymerization technique can enhance the livingness of propagation radicals and kinetic chain length at high monomer conversions for monomers with moderate propagation rate coefficients (k(p)s), reduce the persistent radical effect as much as possible, and hence enable HMWPs without the presence of metal catalyst, exogenous initiator, or harsh equipment. The obtained amphiphilic block copolymers present unique microphase separation behavior, and hold great potential in advanced materials applications, for example, thermosensitive nanocarriers.

Automated summary

A mild organocatalyzed living radical polymerization method was developed to synthesize high molecular weight polymers with low dispersity. This method demonstrated excellent control over molecular weights and dispersity even at high degrees of polymerization. The resulting block copolymers showed unique microphase separation behavior and had great potential in advanced materials applications, such as thermosensitive nanocarriers.