Polymethylene Brushes via Surface-Initiated C1 Polyhomologation

Abstract

Surface-initiated polymerization reactions are a powerful tool to generate chain-end-tethered polymer brushes. This report presents a synthetic strategy that gives access to structurally well-defined hydrocarbon polymer brushes of controlled molecular weights, which can be further modified to generate more complex surface-attached polymer architectures. The hydrocarbon brushes reported in this study are polymethylene brushes that are obtained via surface-initiated C1 polyhomologation of dimethyl­sulfoxonium methylide. The strategy outlined here is based on the use of an alkylboronic acid pinacol ester initiator, which allows for controlled, unidirectional chain growth by monomer insertion into only the C–B bond of the initiator and which presents the polymerization active group at the growing polymer chain end. This surface-initiated C1 polyhomologation methodology is compatible with photopatterning strategies and can be used to generate micropatterned polymethylene brush films. Furthermore, conversion of the boronic ester chain-end functionalities to hydroxyl groups allows for selective chain-end modification and enables access to a variety of surface-anchored block copolymer architectures by chain extension via, for example, ring-opening or atom transfer radical polymerization chemistries.

Molecular Dynamics Simulations of Ideal Living Polymerization: Terminal Model and Kinetic Aspects

“…Next, we focus on σ g in the range of 0.05–0.3σ –2 where all initiators can get reacted (Figure b), corresponding to 0.313–1.875 nm –2 for σ ≈ 0.4 nm that covers typical polymer grafting densities in experiments (e.g., 0.5–1.0 nm –2 ). ,, Figure shows the progression of the chain length distribution along with increasing N̅ . Specifically, the distribution curve shifts along with its primary peak to large N during the polymerization at σ g = 0.05 in Figure a (same as in bulk, Figure ).…”

“…For instance, the commonly used size exclusion chromatography (SEC) analysis can overestimate the width of MWD and dispersity of polymers, especially for those with narrow chain length distribution, due to the intrinsic band-broadening effect . Accurately measuring the MWD of formed brush polymers in the case of surface-initiated polymerization is even more difficult, as the measurement typically requires the cleavage of the brush layer from the substrate while it is hard to collect the cleaved polymers. , In this regard, the development of numerical simulations plays an important role in presenting computational experiments and providing complementary information for a more comprehensive description of polymerization processes and properties of obtained polymers. − …”

“…18 Accurately measuring the MWD of formed brush polymers in the case of surface-initiated polymerization is even more difficult, as the measurement typically requires the cleavage of the brush layer from the substrate while it is hard to collect the cleaved polymers. 12,19 In this regard, the development of numerical simulations plays an important role in presenting computational experiments and providing complementary information for a more comprehensive description of polymerization processes and properties of obtained polymers. 20−23 Molecular modeling and simulations, including molecular dynamics (MD), 24−33 lattice Monte Carlo (MC), 34−41 offlattice MC, 42−44 and dissipative particle dynamics (DPD), 45−47 are conducted to investigate various polymerization schemes, offering detailed molecular-level pictures that significantly enhance our understanding of the polymerization mechanisms.…”

Opportunities, Challenges, and Pitfalls in Making, Characterizing, and Understanding Polymer Brushes

“…The second approach to analyze film thicknesses of solvent-swollen polymer brushes is based on the Alexander–de Gennes theory, which predicts that α = ( d / a ) 3 − 1 / v where α is the swelling ratio ( h swollen / h dry ), d is the distance between anchoring sites of the neighboring surface attached polymer grafts, a is the monomer size, and ν is a factor which approximates 3/5 for a semidilute brush, but for a densely grafted brush is usually taken as 0.5 in a theta solvent. , From this expression, σ is obtained as 1/ d 2 . This method has been used to characterize the grafting density of PNIPAM, poly(ethyl methacrylate) (PEMA), poly(2,2,2-trifluoroethyl methacrylate), poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate), and poly(2-perfluoro­octylethyl methacrylate) brushes , prepared by SI-ATRP, as well as of polymethylene brushes, which were obtained using surface-initiated C1 homologation …”

Miniemulsion SI-ATRP by Interfacial and Ion-Pair Catalysis for the Synthesis of Nanoparticle Brushes

“…Recent advances in macromolecular chemistry enable the preparation of well-defined organic–inorganic hybrid materials. − These materials are mostly surface-modified silica nanoparticles (NPs) with tethered organic polymers, forming silica–polymer core/shell nanohybrids. − Control over the (co)­polymer brushes (monomer types, , brush length, dispersity, − compositions, etc .) attached to the inorganic particle surface results in precisely controlled nanocomposite materials.…”