Atomistic Structure of Bottlebrush Polymers: Simulations and Neutron Scattering Studies

Abstract

We have used small angle neutron scattering (SANS) measurement and atomistic molecular dynamics (MD) simulations to investigate the conformation of bottlebrush polymers with poly(norbornene) (PNB) backbone and different sizes of poly(lactide) (PLA) side chains (PNB 25 -g-PLA 5 , PNB 25 -g-PLA 10 , and PNB 25 -g-PLA 19 ). At early stage of simulations, stretched side chains with visible spatialcorrelations of about 30 Å were observed. The experimentally measured SANS data, on the other hand, does not exhibit any correlation peaks in the corresponding length scale indicating a compact form rather than a stretched-hairy polymer conformation. As the simulation continued, the spatial correlations between side chains disappeared after about 40 ns of chain relaxation, and the scattering intensity calculated for the simulated structure becomes reasonably close to the measured one. Statistical approach is used to overcome the time scale limitation and search for optimal conformation space, which also provides a good agreement with the experimental data. Further coarse-grained simulation results suggest that the side chain conformation strongly depends on the solubility competition among side chain, backbone, and solvent. Significant changes of backbone dynamics due to the side chain encapsulation have been revealed and discussed.

Scaling Laws of Bottle‐Brush Polymers in Dilute Solutions

“…However, there remains inconsistency in the current interpretations of these systems, which is clearly seen in the deviation of simulated and experimental observations from the theoretical predictions and also from each other . One of the difficulties in analyzing the simulation studies is that, due to the increase in computational effort with increasing numbers of side‐chain monomers, the typical polymer lengths considered are much shorter than those in experiments . More importantly, due to the complexity of the structural ensembles generated by bottle‐brush polymers, it is not clear whether well‐defined scaling relations can be observed for the relatively coarse metrics that are typically employed, such as end‐to‐end distance ( R e ) and radius of gyration ( R g ) of the entire polymer.…”

“…Variations of the grafting intervals as well as side‐chain and backbone lengths lead to an interplay of monomer excluded volumes, which in turn gives rise to an intricate adaptation of structures . Several experimental and theoretical studies have been performed to probe these complicated structural features . Often, these studies characterize the structures by identifying different scaling regimes with the goal of validating the theoretical prediction] (where is the persistence length of the backbone and N s is the number of monomers present in each side‐chain of the bottle‐brush polymer).…”

Hierarchical excluded volume screening in solutions of bottlebrush polymers

“…Given that the properties of bottlebrushes are very distinct in comparison to linear polymers, they have been an active field of exploration for numerous theoretical [36][37][38][39][40][41][42][43][44][45][46][47][48], experimental [16,[49][50][51][52][53][54][55][56][57][58][59][60][61][62][63], and numerical investigations [38,47,48,55,[64][65][66][67][68][69][70][71][72][73][74]. A majority of these studies has focused on basic structural properties in solutions and in the adsorbed state.…”

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

“…[290], polylactate groups [291,292,293], polypeptide chains [294], polyacrylate or substituted polystyrene chains [295], nitroxide groups [296], fluorescent groups [297], a perfluorooctyl group [298], perfluorocarboxylic acid groups [299], and a fullerene-carbene adduct [300]; (2) norbornene in the presence of Fe 3 O 4 nanoparticles [301]; (3) norbornenes in the presence of an allylated lanthanide salen complex [302]; (4) norbornyl-acac-like systems complexed to terbium [303] or to an iridium-pyrazolone complex (e.g. 71) [304];…”