Thermolysis of RAFT-Synthesized Poly(Methyl Methacrylate)

Abstract

Thermolysis provides a simple and efficient way of eliminating thiocarbonylthio groups from RAFT-synthesized polymers. The course of thermolysis of poly(methyl methacrylate) (PMMA) prepared with dithiobenzoate and trithiocarbonate RAFT agents was followed by thermogravimetric analysis (TGA), 1 H NMR spectroscopy, and gel permeation chromatography (GPC). The weight loss profile observed depends strongly on the RAFT agent used during polymer synthesis. PMMA with a methyl trithiocarbonate end group undergoes loss of that end group at ∼180 • C, at least in part, by a mechanism believed to involve homolysis of the C-CS 2 SCH 3 bond and subsequent depropagation. In contrast, PMMA with a dithiobenzoate end appears more stable. Only the end group is lost at ∼180 • C and the dominant mechanism is proposed to be a concerted elimination process analogous to that involved in the Chugaev reaction.

Living Radical Polymerization by the RAFT Process - A Second Update

“…[56] The course of the RAFT polymerization of butyl acrylate (BA) and St with cumyl (22) and cyanoisopropyl dithiobenzoate (24) was followed by electron spin resonance (ESR) spectroscopy. [57] 13 C NMR spectroscopy was used to follow the initiation of St polymerization withAIBN-α-13 C and with cumyl (22) and cyanoisopropyl (24) and benzyl dithiobenzoates (61) and with cyanoisopropyl dodecyl trithiocarbonate (121). [51] An unexpected finding was the observation of 13 C chemically induced nuclear polarization (CIDNP) for the ketenimine formed by cage recombination of the AIBN-derived cyanoisopropyl radicals.…”

“…[94] Thermolysis The thermal stability of RAFT-synthesized PMMA has been studied by several groups. [116,121] PMMA with a methyl trithiocarbonate end-group undergoes loss of that end-group at ∼180 • C, at least in part, by homolysis of the C-CS 2 SCH 3 bond and subsequent depropagation. [121] In contrast, PMMA with a dithiobenzoate end appears more stable.…”

“…[116,121] PMMA with a methyl trithiocarbonate end-group undergoes loss of that end-group at ∼180 • C, at least in part, by homolysis of the C-CS 2 SCH 3 bond and subsequent depropagation. [121] In contrast, PMMA with a dithiobenzoate end appears more stable. Only the end-group is lost at ∼180 • C and the dominant mechanism is proposed to be a concerted elimination process analogous to that involved in the Chugaev reaction (Scheme 8).…”

“…Only the end-group is lost at ∼180 • C and the dominant mechanism is proposed to be a concerted elimination process analogous to that involved in the Chugaev reaction (Scheme 8). [121] Thermal elimination of the end-groups from PSt or PBA with secondary xanthate end-groups occurs at relatively low temperatures. It is proposed that the elimination proceeds selectively to produce a polymer with a thiol chain end also by a Chugaev mechanism (Scheme 9).…”

Sequential thiol‐ene/thiol‐ene and thiol‐ene/thiol‐yne reactions as a route to well‐defined mono and bis end‐functionalized poly(N‐isopropylacrylamide)

“…As such, RAFT offers an attractive, and convenient, route to telechelic (co)polymers simply via the use of functional RAFT agents. 47 In addition, the thiocarbonylthio end-groups are easily modified postpolymerization to a variety of species including cleavage to a thiol, typically with a primary or secondary amine, 5,48,49 cleavage to a thiolate, 50,51 thermolysis to an ene, 52,53 or radicalinduced reduction to a saturated species with, for example, Bu 3 SnH. 54 Importantly, the presence of the reactive thiol, or thiolate, at the x chain terminus allows for further modification reactions to be performed via the versatile thiol-ene chemistry.…”