Exploring Quality in Gradient Copolymers

Abstract

Quality of gradient copolymers is evaluated by atomic force microscopy (AFM) and correlated with molecular weight distribution (MWD) values. ARGET ATRP is employed with decreasing levels of catalyst concentrations to generate copolymers with increasing M¯w/M¯n values. The copolymers are transformed into molecular bottlebrushes to enable imaging and analysis of individual molecules by AFM. The average height (cross-sectional) profile of all bottlebrushes agrees with the instantaneous composition (ICHEMA-TMS ) of the analogous copolymer backbone, as determined by (1) H NMR. The copolymer synthesized with 500 ppm of catalyst exhibits more narrow distributions of both brush height and backbone length when analyzed as a bottlebrush by AFM. Correspondingly, the copolymers synthesized with lower catalyst concentrations yield bottlebrushes with broader height and length distribution. These results establish MWD values as an excellent trait to assess quality within gradient copolymers.

Asymmetric Copolymers: Synthesis, Properties, and Applications of Gradient and Other Partially Segregated Copolymers

“…Finally, a method has been developed to experimentally determine gradient quality under the very specific circumstance where one of the monomers can be used as an initiator for a subsequent polymerization, leading to the formation of a bottlebrush . In this case, individual molecules can be visualized by atomic force microscopy (AFM) ( Figure ), and the density of functionalization evaluated as a function of chain length.…”

“…In this case, individual molecules can be visualized by atomic force microscopy (AFM) ( Figure ), and the density of functionalization evaluated as a function of chain length. Using this technique, Matyjaszewski and co‐workers propose the standard deviation of the instantaneous composition <s> as a measure of gradient quality (Equation , where h i and h a represent the height of an individual chain and the average height of all chains, respectively, as measured by AFM). …”

“…AFM height image with top‐ and side‐view representations of gradient molecular bottlebrushes on a surface. Reproduced with permission . Copyright 2013, Wiley‐VCH.…”

Synthesis of Bottlebrush Polystyrenes with Uniform, Alternating, and Gradient Distributions of Brushes Via Living Anionic Polymerization and Hydrosilylation

“…The bottlebrush polymers have been defined as multiple polymeric brushes which are densely grafted onto a polymer backbone . Due to their unique structures and properties, bottlebrush polymers are greatly applied in self‐assembly, nanomaterials, etc . It thus had sparkled interests among polymer chemists to design and synthesize well‐defined bottlebrush polymers.…”

“…Click reaction is then carried out to synthesize bottle brushes (co)polymers efficiently . Branched distributions can be controlled and gradient bottlebrushes are synthesized and characterized clearly, showing unique stretch structures …”