Swelling‐Induced Chain Stretching Enhances Hydrolytic Degrafting of Hydrophobic Polymer Brushes in Organic Media

Abstract

Hydrophilic polymer brushes grown via surfaceinitiated polymerization from silicon oxide surfaces can detach or degraft in aqueous media. Degrafting of these chain endtethered polymers is believed to involve hydrolysis of bonds at the polymer-substrate interface.Degrafting so far has not been reported for hydrophobic polymer brushes in non-aqueous media. This study has investigated the degrafting and swelling properties of poly(tert-butyl methacrylate) (PtBMA) brushes in different water-miscible,organic solvents,viz. DMF,acetone and THF.Inthe presence of asufficient quantity of water in the organic solvent, degrafting was also observed for PtBMA brushes.M ore importantly,h owever,t he rate of degrafting depended on the nature of the organic solvent and the apparent initial rate constant of the degrafting reaction was found to correlate with the swelling ratio of the polymer brush in the different solvents.T his correlation is first, direct evidence in support of the hypothesis that degrafting is facilitated by atension that acts on the bond(s) that tether the polymer chains to the surface and whichi sa mplified upon swelling of the polymer brush. Scheme 1. Preparation of PtBMA brushes via SI-ATRP.

Hydrolysis-resistant heterogeneous photocatalysts for PET-RAFT polymerization in aqueous environments

“…Based on studies outlined above by Genzer, 63 de Beer, 64 and Klok, 65 we hypothesized that hydrolysis of the –Si–O– bonds, connecting the polymer brush to the glass beads, is occurring (Fig. 2a) due to the ingress of water into the brush/glass interface.…”

“…This would contaminate the synthetic product and decrease the ability to efficiently recycle the photocatalysts. Indeed, polymer brushes cleaving from surfaces due to silane hydrolysis has previously been studied by Genzer, 63 de Beer, 64 and Klok, 65 all of whom identied noticeably decreased graing densities over timeeven in humid air. Previous studies [66][67][68] indicate however that a hydrophobic polymer shell can act as a protective barrier to limit diffusion of water molecules to the polymer/glass interface and prevent polymer brush hydrolysis.…”

Spontaneous Degrafting of Weak and Strong Polycationic Brushes in Aqueous Buffer Solutions

“…[14][15][16][17][18][19] Several researchers reported on degrafting of hydrophilic polymer brushes in aqueous solution 20,21 and even degrafting of hydrophobic polymers in organic solvents. 22 Polymer brush degrafting involves a breakage of a covalent bond in the initiator linker with the assistance of a mechanical force due to swelling of the brush. 23 Many researchers have attempted to comprehend breaking a covalent bond in grafted polymers to disclose the mechanism of chain breaking by considering click chemistry 24 , photo-cleaving [25][26][27] , sonication-induced chain scission 28,29 , strong acid or base [30][31][32][33] , etc.…”