Facile and versatile platform for the preparation of functional polyethylenes via thiol‐ene chemistry

Abstract

Polyethylene (PE) is the most used commodity polymer today. The reason PE has found widespread use in a range applications is due to the unique and tuneable properties available by tuning the molecular weight, the degree of branching, and choice of comonomers made by Ziegler-Natta or metallocene chemistry.1 The common industrial techniques used to make PEs have limited versatility to prepare functional PEs with, especially with polar comonomers. However, the range of applications could be increased further with the ability to prepare functional polyolefins.A range of techniques have been developed to prepare functional PE polymers. 3 The Wagner group has developed a number of strategies using acyclic diene metathesis (ADMET) polymerizations. [4][5][6][7][8] Recently, Hillmyer and coworkers 9 developed a two-step synthesis using ring-opening metathesis polymerization (ROMP) of acetoxy functional cyclooctene to produce stereo regular functional polyolefins. A range of functional groups have been incorporated into PE's structure including: phosphonic ester and phosphonic acid, 10 carboxylic acid, 11 amino, 12 alcholol, 13 methylimidazolium bromide. 6Most of the strategies developed require functionalization of monomers. Herein, we describe a versatile platform synthesis whereby the one polymer platform can be functionalized with a number of polar or nonpolar groups.Here, we have taken inspiration from work that has utilized norbornene 14 and internal double bonds produced from ROMP polymers [15][16][17] and poly(butadienes) 18 as functional handles using thiol-ene chemistry; this is a new strategy in the development of a range of functional polyolefins. Our simple and versatile approach to develop functional polyethylenes is based on the preparation of polycyclooctene (P oct ) by ROMP of cyclooctene with Grubbs second generation catalyst. Subsequent functionalization reactions of the internal alkene bond can be achieved with a range of thiol functional molecules, via photoactivated thiol-ene click chemistry to prepare a range of functional PEs,19,20 providing a unique and versatile technique to functionalize PEs.ROMP polymerizations of cyclooctene were performed for 1 h in dichloromethane at 30 C, resulting in a library of polymers with M n ranging from 7 to 165 kDa and typical dispersity index of about 1.6, see Supporting Information Table S1 for details. These versatile platform polymers were used to demonstrate facile functionalization strategies using thiol-ene photochemistry, with a wide range of thiols (Scheme 1). The thiol-ene photoinitiated reactions were performed in appropriate solvents with an excess amount of thiol-containing small molecules (2-5 equivalents per double bond). 2,2-Dimethoxy-2-phenylacetophenone (DMPA) was used as a photoinitiator and irradiated with UV (365 nm) light for 6 h.

Controlling Polymer Composition in Organocatalyzed Photoredox Radical Ring-Opening Polymerization of Vinylcyclopropanes

“…Radical addition, such as thiol–ene “click” reaction, has been used to functionalize polymers containing internal C–C double bonds . The reactive alkene groups periodically spaced along the backbone of poly­(EtVCP) with high l content piqued our curiosity about the stability of this polymer-chain under photoredox conditions and the possibility to cross-link the resulting polymers.…”

Versatile functionalization of aromatic polysulfones via thiol‐ene click chemistry

“…Pristine PSU has high T g of 192 °C. Upon thiol‐ene functionalization, PSU‐TEG‐50 showed the highest decrease of T g at 114 °C due to the incorporation of a long, flexible ethylene glycol ether chain which acts as an internal plasticizer . PSU‐ME‐50 which has the smallest size among the tested thiols showed the smallest decrease of T g (175 °C).…”

Spatial control of flocculation via light

“…Over the past decade, considerable efforts have been made in the area of stimuli‐responsive chemistry which have led to the development of new tailored smart materials . The use of light to modulate stimuli‐responsive systems is a powerful strategy to remotely and accurately control material properties . Thus, efficient photochemical reactions are not only the pursuit of organic and polymer chemistry which demand reactions take place under neutral and reagent‐free conditions, but are also highly applicable in materials chemistry and biology to mediate processes in a spatially and temporally controlled manner .…”

“…1 The use of light to modulate stimuli-responsive systems is a powerful strategy to remotely and accurately control material properties. [2][3][4] Thus, efficient photochemical reactions are not only the pursuit of organic and polymer chemistry which demand reactions take place under neutral and reagent-free conditions, but are also highly applicable in materials chemistry and biology to mediate processes in a spatially and temporally controlled manner. [5][6][7] In this study, we present a highly efficient photoinitiated flocculation system formed through the trapping of a photogenerated thiobenzaldehyde with polyethylenimines (PEIs).…”