Conformational Properties of End-Grafted Bottlebrush Polymers

Abstract

Scaling analysis combined with free-energy calculations and molecular dynamics simulations of a coarse-grained bead-spring model have been used to study the structural properties of planar brushes formed by bottlebrush polymers tethered by ends to a flat surface. We find that the height H of end-grafted bottlebrushes undergoes a sequence of conformational changes emerging from the overlap between molecules at subsequent length scales upon increasing the number of bottlebrushes per unit surface area σ. We establish a relation between H and the structural parameters of bottlebrush architecture: degree of polymerization of backbone N bb and side chains N sc as well as grafting density z of side chains. We find that nonoverlapping bottlebrushes exhibit the behavior of isolated polymers in a good solvent with the height that is σ-independent and scales as ∝ (1 + zN sc)2/5 N bb 3/5. Weakly overlapping bottlebrushes are similar to end-grafted linear polymers (z = 0), and the height in this regime is ∝ σ1/3(1 + zN sc)2/3 N bb. Strongly overlapping bottlebrushes undergo a further increase in height, which is given by ∝ σ2/7 z 6/7 N bb.

Structure of Self-Initiated Photopolymerized Films: A Comparison of Models

“…Grafted polymer architectures with long side chains, called bottlebrushes, have received increased interest recently due to improvements in grafting methods and promising applications. , Similar systems made using PEG 45 MA and HEMA and their interactions with SDS have been studied before, but neutron reflectometry studies were only performed on polyelectrolyte systems where HEMA was substituted with 2-(trimethylammonio)­ethyl methacrylate chloride (METAC) . However, scaling analysis combined with free energy calculations and molecular dynamics simulations of bottlebrushes with increasing grafting density resulted in increasing chain heights even at low and intermediate grafting densities . To assess the relevance of bottlebrush models for approximating the structure of SI-PGP polymers, the chain structure needs to be known, but determining the exact HEMA:PEG 10 MA monomer ratio in the current films is difficult due to lack of contrast between the monomers, which is represented in the large error values for the HEMA content of the films (Table ).…”

“… 70 However, scaling analysis combined with free energy calculations and molecular dynamics simulations of bottlebrushes with increasing grafting density resulted in increasing chain heights even at low and intermediate grafting densities. 71 To assess the relevance of bottlebrush models for approximating the structure of SI-PGP polymers, the chain structure needs to be known, but determining the exact HEMA:PEG 10 MA monomer ratio in the current films is difficult due to lack of contrast between the monomers, which is represented in the large error values for the HEMA content of the films ( Table 3 ). Calculating the weighted average results in 59 ± 16% HEMA content, which is near the HEMA concentration in the monomer solution used for the polymerization, indicating approximately one PEG 10 MA monomer for every other unit on the backbone.…”

Neutron Reflectometry Studies of the Hydrated Structure of Polymer Thin Films

“…The origin of this extra stretching is not clear from the neutron experiments. Here it is attributed to the interaction between the PEG10MA sidechains in a bottlebrush-like manner 149 . However, recent results indicate that PEG may bind with hydronium ions, forming a so-called supra-polyelectrolyte 150 .…”

Implicit Side-Chain Model and Experimental Characterization of Bottlebrush Block Copolymer Solution Assembly

“…Concurrent with experimental efforts, theoretical and computational efforts have sought to predict the relationships between bottlebrush polymer architecture and conformation, and ultimately material properties. ,− Early theoretical efforts used scaling arguments to predict conformations of bottlebrush polymers in dilute solutions under different solvent conditions. − Since these initial studies, a variety of approaches have been used to understand conformational structure and dynamics of bottlebrush polymers, such as general and renormalized perturbation theories, self-consistent-field theory, ,,,− density functional theory, and polymer reference interaction site model (PRISM) theory. ,, Apart from these theoretical methods, the scaling theory remains a useful tool for understanding bottlebrush structure. ,− …”