Polymers with a thermally triggered phase transition are important in the design of materials for biological applications, where their behavior can be used to trigger release or (dis)assembly events. Despite their advantages, a system with tunable thermal response, end-group reactive sites, low toxicity, and controlled main-chain degradability has not been realized, yet this would be a significant advance. The versatile new poly(oligo(ethylene glycol) vinyl acetate)s are presented with excellent control over their molecular properties obtained through RAFT/MADIX polymerization. Furthermore, we demonstrate structure-controlled thermal transitions, conjugation to human lysozyme through the retained end-group, and moreover show that this class of polymers can uniquely be copolymerized with 2-methylene-1,3-dioxepane (MDO) to generate polymers in which the degradability and cloud point can be independently tuned to create materials that display the same cloud point but degrade differently.

Thiolactones allow catalyst-free polymer synthesis and modification under stoichiometric conditions at mild temperatures, without the need for tedious and costly purification steps. However, there is a need for simple and general methods for the preparation of functional thiolactones. We have developed a modular platform for γ-thiolactone synthesis based on free-radical xanthate addition to alkenes. Because of the ready availability of a great variety of functional vinyl, allyl, and maleimido derivatives, numerous substituents (exemplified here through alkyl, perfluoroalkyl, diethyl phosphonate, and N-substituted succinimidyl groups) could be efficiently attached to the γ-position of the thiolactone ring. A second substituent may be added in the α-position by proper selection of the xanthate leaving group. In all cases the target thiolactone was obtained in good yield from the xanthate:alkene monoadduct by consecutive Chugaev elimination and cyclization. The potential of these new substituted thiolactone building blocks for polymer chemistry was demonstrated via an amine–thiol–ene conjugation strategy which resulted in successful end-functionalization of amino-terminated polymers and a thiol–acrylate step-growth polymerization to prepare functional poly­(ester amide)­s. This versatile method for making functional thiolactones should find broad applications as a means to prepare new materials with original properties.

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.

The reactivity of functional γ-thiolactones has been investigated in Ring Opening Copolymerization with trimethylene carbonate.

Anionic polymerization of butadiene or/and styrene is performed with lithium initiators, functional or not. The polymer chains are subsequently transferred to magnesium. The resulting polymeryl-magnesium compounds were combined with {(Me 2 Si(C 13 H 8 ) 2 )Nd(μ-BH 4 )[(μ-BH 4 )Li(THF)]} 2 metallocene complex to act as macromolecular chain transfer agents (macroCTAs) in coordinative chain transfer polymerization (CCTP) of ethylene (E) or its copolymerization (CCTcoP) with butadiene (B). Block copolymers were produced for the first time by this switch from anionic polymerization to CCTP. Hard and soft blocks such as PB, polystyrene (PS), poly(styrene-co-butadiene) (SBR) obtained by anionic polymerization and PE or poly(ethylene-cobutadiene) (EBR) produced by CCT(co)P were combined and the corresponding structures were characterized.

Block copolymers based on ethylene (E) and butadiene (B) were prepared using the ansa-bis(fluorenyl) complex {Me 2 Si(C 13 H 8 ) 2 Nd(BH 4 ) 2 Li(THF)} 2 in combination with (n-Bu)(n-Oct)Mg (BOMAG) as a chain-transfer agent. The diblock copolymers incorporating a soft poly(ethylene-cobutadiene) segment, called ethylene butadiene rubber (EBR), and a hard polyethylene (PE) one were obtained by simply adjusting the different feeds of monomers during the polymerization. The soluble EBR block was formed first by feeding the catalytic system dissolved in toluene at 70 °C with a mixture of ethylene and butadiene (E/B molar ratio 80 : 20).Then the feeding was stopped leading to the consumption of a large part of the residual monomers. The reactor was finally fed with ethylene to form the PE block. By varying the molar mass of the latter, it is shown that the resulting soft-b-hard block copolymers can self-assemble simultaneously to the growth of the PE block in agreement with a polymerizationinduced self-assembly (PISA) mechanism. The self-assembly is discussed considering the reaction conditions, the crystallization of the PE block, and the polymerization mechanism involved.

A modular platform based on free-radical xanthate addition to alkenes enables access to a large series of functional γ-thiolactones. This methodology includes two different pathways based on xanthate chemistry involving radical addition and Chugaev elimination steps. The first method uses the addition of an ester-functionalized xanthate to various commercially functional alkenes, whereas the second one is based on the addition of functional xanthates to an ester-functionalized alkene. In both cases, a series of xanthate/alkene monoadducts was obtained, and their thermolysis and subsequent cyclization led to a library of functional γ-thiolactones in moderate to good yield. For a few cases where it may not be possible to directly incorporate some targeted functional groups via the proposed process involving free radicals and high temperature, a bromo-functionalized thiolactone was used as a starting material for chemical transformations.

The concepts of polymer–peptide conjugation and self-assembly were applied to antimicrobial peptides (AMPs) in the development of a targeted antimalaria drug delivery construct. This study describes the synthesis of α-acetal, ω-xanthate heterotelechelic poly­(N-vinylpyrrolidone) (PVP) via reversible addition–fragmentation chain transfer (RAFT)-mediated polymerization, followed by postpolymerization deprotection to yield α-aldehyde, ω-thiol heterotelechelic PVP. A specific targeting peptide, GSRSKGT, for Plasmodium falciparum-infected erythrocytes was used to sparsely decorate the α-chain ends via reductive amination while cyclic decapeptides from the tyrocidine group were conjugated to the ω-chain end via thiol–ene Michael addition. The resultant constructs were self-assembled into micellar nanoaggregates whose sizes and morphologies were determined by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The in vitro activity and selectivity of the conjugates were evaluated against intraerythrocytic P. falciparum parasites.