Main Chain Conformation and Anomalous Elution Behavior of Cylindrical Brushes As Revealed by GPC/MALLS, Light Scattering, and SFM

Abstract

High molar mass polymacromonomers based on methacryloyl end-functionalized oligo methacrylates (Mn ) 2410 g/mol) adopt the conformation of wormlike cylindrical brushes. Comparison of the absolute molar mass, Mw, determined by static light scattering and the contour length, Lw, of the molecules measured by SFM in the dry state revealed the length per vinylic main chain monomer of the cylindrical structure to be less than 0.1 nm, thus being much shorter than the maximum value of 0.25 nm. In solution this shrinkage could be quantified to 0.071 nm per monomer by Holtzer analysis of the scattering curves which in addition yielded the Kuhn statistical segment length lk ) 120 nm. GPC MALLS investigations of such samples showed an anomalous elution effect: After a regular elution at small elution volumes the molar mass of the eluting molecules increased drastically with increasing elution volume. Fractionation by GPC showed that this effect is caused by a fraction of extremely high molar mass molecules which elute by an unknown mechanism rather than by size exclusion.

Hierarchically organized micellization of thermoresponsive rod‐coil copolymers based on poly[oligo(ethylene glycol) methacrylate] and poly(ε‐caprolactone)

“…41 Moreover, anomalous elution behavior has been demonstrated for other cylindrical brushes. 42 All the polymers showed monomodal distributions and a relatively narrow molecular weight distribution by GPC.…”

Design, Synthesis, and Self-Assembly of Polymers with Tailored Graft Distributions

“…The backbones are drawn in the fully extended limit for ease of visualization, and the side chain conformations and cross-sectional radii are depicted as anticipated by existing theory. 5,[44][45][46] BP-1 was synthesized by first copolymerizing PDMS and endo,exo-norbornenyl dimethylester (dx-DMeE, 1a) in a 1:1 feed ratio. Since r1 = 1.1 and r2 = 0.94, the first block has an ideal random backbone sequence and therefore uniform side chain distribution.…”

“…[39][40][41][42][43] These cylindrical brushes can be modeled as wormlike chains with the same average crosssectional radius (Rc) along the entire backbone. 5,[44][45][46] On the other hand, if the macromonomer and diluent copolymerize at different rates, the resulting gradient sequences are anticipated to template different side chain conformations. Depending on the extent of side chain stretching, Rc varies and tapered, noncylindrical molecular shapes result ( Figure 1B).…”

Ring comb copolymer brushes

“…Subsequently, a number of different comb copolymers have been synthesized along this route and their conformations in dilute solutions as well as in thin films were characterized by scattering techniques and atomic force microscopy. [7][8][9][10][11] In a most recent publication a new methodology was introduced and the synthesis, dimensions and solution properties of linear and macrocyclic poly͑chloroethyl vinyl ether͒-g-polystyrene comblike copolymers ͑PCEVE-g-PS͒ were reported. 12 Experimentally, linear comb copolymers consisting of a flexible backbone densely grafted with flexible side chains have been investigated thoroughly by Schmidt and co-workers.…”

“…12 Experimentally, linear comb copolymers consisting of a flexible backbone densely grafted with flexible side chains have been investigated thoroughly by Schmidt and co-workers. 5,[7][8][9][10][11] Another variant uses so-called dendrons as side groups. 6,13 In general, the presence of a large number of side chains results in severe stiffening of the structure leading to cylindrical comb copolymer brushes ͑or molecular bottle-brushes͒.…”