Supramolecular Polymer Brushes: Influence of Molecular Weight and Cross-Linking on Linear Viscoelastic Behavior

Abstract

The origin of unique rheological response in supramolecular brush polymers is investigated using different polymer chemistries (poly­(methyl acrylate) (PmA) and poly­(ethylene glycol) (PEG)), topologies (linear or star), and molecular weights. A recently developed hydrogen-bonding moiety (1-(6-isocyanatohexyl)-3-(7-oxo-7,8-dihydro-1,8-naphthyridin-2-yl)-urea) (ODIN) was coupled to PmAs and PEGs to form supramolecular brush polymers, the backbone of which is formed by the associated moieties. At low molecular weights of monofunctionalized polymers (both PmA and PEG), the formed brushes are mostly composed of a thick backbone (with very short arms) and are surrounded by other similar brush polymers, which prevent them from diffusing and relaxing. Therefore, the monofunctionalized PmA with a low M n does not show terminal flow even at the highest experimentally studied temperature (or at longest time scales). By increasing the length of the chains, supramolecular brushes with longer arms are obtained. Due to their lower density of thick backbones, these last ones have more space to move and their relaxation is therefore enhanced. In this work, we show that despite similarities between covalent and transient brush polymers, the elastic response in the latter does not originate from the brush entanglements with a large M e (entanglement molecular weight), but it rather stems from the impenetrable rigid backbone and caging effect similar to the one described for hyperstars.

Hydrogen Bonding in Self-Healing Elastomers

“…The mechanical strength of a (UPy) 3 T film can recover even after 5 s in water at 70 °C because of the high multiple hydrogen-bonding interaction and the semicrystalline properties. Another self-healing material with multiple hydrogen bonding as terminal units is developed by Loos and co-workers, as shown in Figure 6 d. 56 …”

Shear Thinning from Bond Orientation in Model Unentangled Bottlebrush Polymer Melts

“…This is complicated by the challenges in the controlled synthesis and characterization of branched polymers. 29,30 Several studies have been conducted to investigate the rheological properties of melts or solutions of bottlebrushes (synthetic or biological) such as their viscoelasticity, 31,32 shearinduced crystallinity, 33,34 and shear-thinning behavior in aggrecan solutions. 35 A few experimental studies shed light on the complex contribution of the bottlebrush architectural parameters to their melt rheology.…”

Scalable and Degradable Dextrin-Based Elastomers for Wearable Touch Sensing

“…However, their synthetic strategies often require complex and costly procedures, impeding commercialization. 17,18 Most importantly, most of these bottlebrush polymers are made of nondegradable acrylates, so clever macromolecular design is required to replace both backbone and side chains with appropriate bio-based materials.…”

“…Bottlebrush polymers offer an opportunity into low modulus elastomers with high stability because of their densely dispersed dangling chains (full crosslinking is not necessary), showing promises for wearable applications. However, their synthetic strategies often require complex and costly procedures, impeding commercialization. , Most importantly, most of these bottlebrush polymers are made of non-degradable acrylates, so clever macromolecular design is required to replace both backbone and side chains with appropriate bio-based materials.…”