A Method for Characterizing the Chemical Heterogeneity of Comb-Copolymers and Its Dependence on Synthesis Routes

Abstract

The heterogeneity in chemical structure of polymers is difficult to characterize and consequently remains an often-overlooked factor in mechanistic studies of functional polymers, as well as in their industrial scale optimization. In this study, we present a method to characterize chemical heterogeneity and apply it to illustrate how it can be affected differently in different synthesis routes. The polymers used are comb-copolymer dispersants used in particulate suspensions which are composed of a polycarboxylate backbone onto which PEG side chains are grafted. The largest use of these polymers concerns concrete, where they are referred to as poly(carboxylate ether) (PCE) superplasticizers and produced at a very large industrial scale. Apart from their practical relevance, PCEs provide a good test case for studying the means and benefits of characterizing chemical heterogeneity. Indeed, the simple addition of a UV detector to a traditional SEC setup with RI detection allowed us to monitor variations in the grafting ratio in dependence on the molecular size. We show that the synthesis pathway significantly impacts the chemical heterogeneity. The suggested method is versatile and can be adapted for a wide range of hydrophilic copolymers. Thus, we present a tool to comprehensively analyze the molecular heterogeneity of dispersants and give a deep insight into their chemical dispersity.

Research needs for cementitious building materials with focus on Europe

“…An often-overlooked parameter is the polydisperse nature of PCEs. Such heterogeneity can arise from the synthesis method (free radical copolymerization (FRC) vs polymer analogous esterification (PAE)) and within each method, from the synthesis route applied as shown in [83]. Such polymer reactions result in a cocktail of polymers having both variations in grafting densities and masses especially with the FRC route which is the main industrial route for PCE production.…”

Rheological Investigation of a Set of PCE Superplasticizers in Cement

“…Note that a repeat unit comprises the side chain monomer and (N-1) charge-carrying monomers. The molecular weight of the macromonomer determines P. Finally, the CTA amount and the initiator concentration influence the backbone length n. The chemical structure analysis of the obtained PCE can be challenging [3,4]. Gel permeation chromatography (GPC) gives insight into the molar mass distribution of the resulting PCE molecules but does not provide information about the monomer distribution within the polymer chains.…”

Influence of Pentaerythritol Tetraacrylate Crosslinker on Polycarboxylate Superplasticizer Performance in Cementitious System

“…In general, the PC molecules show a comb-like structure, which consists of a linear backbone with polyethylene glycol side chains and carboxylate [7][8][9][10]. The PC molecules could adsorb on the surface of cement particles, thereby hindering the aggregation of cement particles due to the steric hindrance of the long polyethylene glycol chains [11][12][13][14]. With the increasing demand for the performance of commercial concrete, it is very important to develop PCs with novel structure to satisfy the practical application requirements.…”