Synthesis of Gradient Copolymer Grafted Particle Brushes by ATRP

Abstract

Linear poly(n-butyl acrylate)-gradient-poly(methyl methacrylate) (PBA-grad-PMMA) copolymers and SiO 2 -g-PBA-grad-PMMA particle brushes were synthesized by activator regenerated by electron transfer atom transfer radical polymerization via a semibatch copolymerization method in which the methyl methacrylate (MMA) monomer was slowly fed to the polymerizing n-butyl acrylate (BA) solutions. The effects of initial BA concentration and the MMA feeding rate on the polymerization were investigated. Controlled gradient compositions were achieved at relatively low conversion, <20%. Two gradient copolymer particle brushes, with grafting densities of 0.55 and 0.126 chains/nm 2 , and one linear gradient copolymer were prepared with the same composition. Significant changes were observed after attaching the gradient copolymer ligands onto the surface of SiO 2 nanoparticles, in both thermal and mechanical properties. Greater heterogeneity and microphase separation were introduced after the addition of SiO 2 nanoparticles, and the nanocomposites displayed more complex glass transition temperature (T g ) behavior and a broader T g range. An improvement in mechanical properties (strength and stiffness) was observed as the SiO 2 nanoparticle content increased in gradient copolymer particle brushes; however, the damping property was compromised with increasing stiffness of the materials, especially under low frequency conditions.

One-step synthesis of sequence-controlled multiblock polymers with up to 11 segments from monomer mixture

“…16 – 19 ). This catalysis, involving a five-component mixture, remains highly selective, almost without the tapered region 14 , 43 , 44 , as clearly indicated by the plots of monomer conversion as a function of time (Supplementary Fig. 17 ).…”

Topologically Induced Heterogeneity in Gradient Copolymer Brush Particle Materials

“…The tethering of polymer chains to the surface of nanoparticles to form “brush particles” (aka “hairy particles”) has been shown to provide one-component hybrid materials with improved properties such as biocompatibility, enhanced thermal conductivity, or dielectric breakdown strength that depends on the architecture and composition of the brush particle system. − Recent advances in the surface-initiated controlled radical polymerization (SI-CRP) significantly expanded the control over structural parameters of surface-bound polymer ligands, such as degree of polymerization, dispersity, or grafting density. ,− This enabled the synthesis of brush particle systems with structural and dynamical properties that are tunable across the range of soft (polymer-like) to hard (particle-like) interactions. , Other advantageous features of SI-CRP include the ability to control the chain architecture via the concurrent or sequential reaction of distinct monomers, thus enabling the synthesis of random, gradient, or block copolymer brushes. − Copolymerization affords new opportunities to design the structure and properties of brush particle-based materials. Elucidation of the structure–property relations in copolymer brush particle systems with varied architecture therefore not only promises new insights into the physics of microstructured colloidal systems but also holds opportunities for the design of hybrid materials with novel functionalities.…”

Solution properties of spherical gold nanoparticles with grafted DNA chains from simulation and theory

“…The grafted density must ultimately be limited by the formation of a "brushlike" layer having a nearly uniform polymer segmental density, in which case the polymer-grafted NP becomes effectively similar to a hard sphere. This limiting hard sphere behavior can be achieved in the microemulsion derived NPs mentioned above in the limit of high grafting density [33][34][35][36] or in polymer grafted NPs when the grafted polymer chains are grown directly from the surface of the NPs 57,58 . However, the physical nature of the grafted polymer layer formed by grafting the polymer chains onto the NPs from solution has a rather different structure in which both the grafted ssDNA chains, and the grafted layer of the NP as a whole, exhibit appreciable conformational fluctuations (see snapshots of the simulated polymer grafted NPs in the inset of Figure 2 a).…”