Pinching Dynamics of Telechelic Associating and Coupling Polymers

Abstract

Telechelic associating polymers, TAPs, have numerous industrial applications and are typically evaluated at different concentrations and by their shear viscosity. Here, in situ UV irradiation is added to a dripping-onto-substrate rheometer. TAPs with telechelic coumarin end groups would undergo UV-induced coupling, leading to additional step polymerization of TAPs. This enables us to in situ increase the molecular weight of TAPs without changing concentrations. Their extensional rheology is studied from the recorded pinching process. Extensional viscosities in the elastocapillary state are 10 times higher than those in the viscocapillary state, indicating significant chain stretching. With increasing molecular weights or degrees of coupling, the evolution of capillarity, inertia, viscous, and elastic behaviors is captured by the dimensionless Ohnesorge number and intrinsic Deborah number. The narrow region of a beads-on-a-string structure is also mapped experimentally. Using telechelic associating and coupling polymers as a model system, we have illustrated the evolution of their extensional behaviors as the molecular weight increases.

Pinching dynamics, extensional rheology, and stringiness of saliva substitutes

“…The elastocapillary regime, associated with an exponential decay appears as a straight line on this semi-log plot, and is then curtailed by appearance of the terminal viscoelastocapillary (TVEC) regime that arises due to finite extensibility effects. For the OR series, the IC-VC-EC transition could be due to the role played by associative interactions between the grafted oligomers 70,88,89 or with ingredients like proteins and poloxamer 407 that can complex with polysaccharides via hydrogen bonding, hydrophobic, or electrostatic interactions. 71 As some substitutes contain more than one macromolecular ingredient (see ESI, † for the full ingredient list), the multiple regimes could arise due to progressively contributing components.…”

“…Unlike CaBER or Trimaster or FISER, the DoS protocols involve no moving parts and therefore, allow analysis of low viscosity and low elasticity fluids as the same interplay of stresses that is relevant for jetting, CaBER or dripping drives capillarity-driven pinching dynamics in DoS rheometry. The robustness and utility of this frugal technique has resulted in its increasing use for studying the extensional rheology response of polymer solutions and macromolecular biological fluids, 88,89,153,154,[171][172][173][174][175][176][177] but a thorough examination of the influence of interfacial rheology, complexation between polymers and other ingredients, and adsorption kinetics are also warranted.…”

A Telechelic Fluorescent Indicator Based on Polymer Conformational Change for Free Copper(II) Ions

“…In this paper, we prepared functionalized pNIPAM using radical addition fragmentation transfer (RAFT) [25]. One advantage of RAFT is that the polymer chain is easy to modify, so we could place the desired functionality on the polymer chain [26,27]. Another is that the chain length of the polymer can be tuned.…”