Thiolactone-Functional Reversible Deactivation Radical Polymerization Agents for Advanced Macromolecular Engineering

Abstract

The development of innovative, easy to implement strategies for polymer synthesis and modification contributes to pushing back the limits of macromolecular engineering. In this context, thiolactones were highlighted as a new powerful “click” strategy involving an amine–thiol–ene conjugation. In order to further explore the potential of thiolactone chemistry for the field of reversible-deactivation radical polymerization (RDRP), we have developed a toolbox of γ-thiolactone-based RDRP agents including xanthates, bromides, and an alkoxyamine. These RDRP agents were used for the polymerization of more activated and less activated monomers using appropriate RDRP techniques such as RAFT/MADIX, ATRP, and NMP. Well-defined thiolactone-terminated polymers were obtained and characterized for different degrees of polymerizations. An example of thiolactone–telechelic PNIPAM using a thiolactone-based xanthate and an ω-end-chain cyclization strategy was reported. The great reactivity of the thiolactone end-group for postpolymerization modification was proven using primary amines such as benzylamine or propargylamine, which ring-opened the thiolactone with subsequent thiol–thiolsulfonate reaction to scavenge the generated thiol. The original S-naphthalene ethanethiosulfonate was used to give fluorescence properties to the polymers.

Scope and Limitations of Xanthate-Mediated Synthesis of Functional γ-Thiolactones

“…30 TL15 was obtained from 10-undecen-1-ol and proved its usefulness as a platform for the introduction of several new functions such as secondary and tertiary bromides, xanthates, and an alcoxyamine. 30 These thiolactones were then used as reversible-deactivation radical polymerization agents for atom transfer radical polymerization, reversible addition-fragmentation chain transfer polymerization and nitroxide-mediated polymerization, and nitroxide-mediated polymerization for the synthesis of a diversity of thiolactone-terminated polymers of controlled chain length and narrow molar mass distribution. 30 We evaluated the possibility of shortening the length of the spacer between the hydroxyl group and the thiolactone ring.…”

“…30 These thiolactones were then used as reversible-deactivation radical polymerization agents for atom transfer radical polymerization, reversible addition-fragmentation chain transfer polymerization and nitroxide-mediated polymerization, and nitroxide-mediated polymerization for the synthesis of a diversity of thiolactone-terminated polymers of controlled chain length and narrow molar mass distribution. 30 We evaluated the possibility of shortening the length of the spacer between the hydroxyl group and the thiolactone ring. We selected allyl alcohol, 3-buten-1-ol, and 7-octene-1,2-diol to be reacted with either XA1 or XA2 or with both.…”

RAFT-Based Polymers for Click Reactions

“…The conversion of thiocarbonylthio moiety in the ZC(=S)S group occurs through reactions with appropriate nucleophiles [ 104 , 105 , 106 , 107 , 108 , 109 , 110 , 111 , 112 , 113 , 114 , 115 , 116 , 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 , 126 ] ( Table 2 ) that include mainly primary amines [ 105 , 106 , 107 , 108 , 109 , 110 , 111 , 112 , 113 , 114 ] and hydrazine (or hydrazine hydrate) [ 116 , 117 , 118 , 119 , 120 , 121 ], alkali [ 122 ], and NaN 3 [ 115 ], along with reducing agents such as NaBH 4 [ 123 , 124 , 125 , 126 , 127 ] and LiB(C 2 H 5 ) 3 H [ 128 ]. The choice of the nucleophile depends on the chemical nature of the stabil...…”

The reaction of potassium xanthates with five-membered cyclic carbonates: selectivity of the underlying cascade reactions and mechanistic insights

“…6 The latter methodology has been further expanded by Zard to include not only primary, tertiary and a,a-triuoromethylaminyl radicals [7][8][9] but also to demonstrate some novel radical cascade reactions of xanthates. 10,11 The synthesis of various functional compounds, including g-thiolactones, [12][13][14] pyridine alkaloid xestamines, 15 thiopyranones, 16 thiophenes, 17 dichloroketones, 18 etc., based on free-radical xanthate addition to alkenes has been described in numerous recent works by Zard and Destarac.…”