Conformation of the backbone of bottlebrush polymers

Abstract

Bottlebrush polymers are a hierarchal arrangement of linear polymer chains into two domains: the side chain domain (which disfavors crowding) densely grafted onto a backbone domain (which resists stretching). The net result of the interactions between the two domains is a relatively expanded conformation of the backbone. Despite numerous theor., simulation and exptl. approaches, there is still controversy on the soln. behavior of bottlebrush polymers. Exptl., a main problem can be attributed to limitations that result from the complex architecture; isolating the behavior of each domain is very difficult. Therefore, exptl. detn. on each domain thus far has only been inferred from the overall structure as opposed to being directly measured. Using small-angle neutron scattering (SANS) and selective deuterium labeling, we obtained exptl. conformation of the backbone domain alone. To our knowledge, we are the first to obtain these results. The current accepted model in literature was developed by Birshtein et al. in 1985, which is a self-avoiding walk of 'super' blobs. Our SANS results build on to this exceptional model and provides addnl. insight that has not yet been discussed in literature in the bottlebrush context.