Synthesis of Molecular Brushes with Gradient in Grafting Density by Atom Transfer Polymerization

Abstract

Macromolecular brushes with a gradient of side-chain spacing along the backbone have been synthesized by the "grafting from" approach using atom transfer radical polymerization. A macroinitiator was prepared in two steps, first by conducting a gradient copolymerization of MMA and HEMA-TMS followed by transformation of the resulting poly(MMA-grad-HEMA-TMS) to poly(MMAgrad-BPEM). The gradient composition of the macroinitiator was a forced gradient formed by continuous feeding of HEMA-TMS during MMA polymerization. The gradient structure was characterized by monitoring monomer conversion (GC) and molecular weight evolution (GPC) during copolymerization. AFM measurements demonstrated the characteristic anisotropy of the molecular structure by resolving individual brush molecules with a bulky head and a thin tail.

Structure, function, self-assembly, and applications of bottlebrush copolymers

“…An advantage of the grafting-from approach is that bottlebrushes with very long backbones can be prepared. The grafting density can also be controlled by co-polymerizing two monomers during backbone synthesis 18 . Also, block copolymer side-chains can be incorporated in a straightforward way through sequential polymerization reactions, resulting in core-shell type bottlebrushes 19 .…”

Statistical copolymers of 2‐(trimethylsilyloxy)ethyl methacrylate and methyl methacrylate synthesized by ATRP

“…11 The purpose of this work is to establish the reactivity ratios of 2-(trimethylsilyloxy)ethyl methacrylate (TMSOEMA, monomer M 1 ) and methyl methacrylate (MMA, monomer M 2 ) and to prepare a gradient copolymer with different composition from that prepared by copolymerization of MMA and 2-hydroxyethyl methacrylate (HEMA), using the trimethylsilyl protecting group on 2-hydroxyethyl methacrylate. We note that while poly(TMSOEMA-co-MMA) gradient copolymers have recently been synthesized by Boerner et al, 12 monomer reactivity ratios have not been reported in that work. We first describe the synthesis and characterization of gradient copolymers of TMSOEMA and MMA.…”

“…Usage of common types of catalyst (e.g., CuCl/PMDETA) resulted in hardly controlled process. 22 Thus, trimethylsilyl masking group on HEMA allows using common and well-examined catalytic systems and conditions 12,23 for synthesis of copolymers containing HEMA units (after the hydrolysis of the trimethylsilyl masking groups) by ATRP.…”

Hierarchically organized micellization of thermoresponsive rod‐coil copolymers based on poly[oligo(ethylene glycol) methacrylate] and poly(ε‐caprolactone)

“…6 The combination of this method with grafting approaches has been successfully used to prepare molecular brushes. [7][8][9] In particular, macromonomer polymerization offers advantages on the control of both side chain polydispersity and grafting density over ''grafting onto'' and ''grafting from'' strategies. [10][11] For instance, polymers of high branch density and uniform branch length can be obtained, which would not be easy to prepare by other synthetic approaches.…”