Anomalous Swelling Behavior of Poly(N-vinylimidazole)-l-Poly(tetrahydrofuran) Amphiphilic Conetwork in Water Studied by Solid-State NMR and Positron Annihilation Lifetime Spectroscopy

Abstract

Poly(N-vinylimidazole) homopolymer (PVIm) and poly(N-vinylimidazole)-l-poly(tetrahydrofuran) (PVIm-l-PTHF), a novel amphiphilic polymer conetwork (APCN), were synthesized to compare their solid state structure and investigate the swelling behavior of this unique conetwork in water. A short-range ordered structure stabilized by second-order interactions between the imidazole pendant groups was found in the PVIm homopolymer and in the PVIm phase of the dry conetwork as revealed by solid-state NMR 13 C cross-polarization magic angle spinning (CP MAS) and two-dimensional 1 H− 13 C frequencyswitched Lee−Goldburg (FSLG) HETCOR measurements. With increasing swelling ratio, structural and conformational changes were recognized in the hydrophilic PVIm phase of the APCN. In the kinetic swelling study, unexpectedly, four different swelling ranges were identified by gravimetric measurements, solid-state NMR methods, and positron annihilation lifetime (PAL) spectroscopy before the APCN reached its equilibrium swelling state. In the first period, which takes place in several minutes, the ordered structure disintegrates in the PVIm phase and the water uptake is relatively slow. This structural realignment is followed by the main course of water uptake governed by Fickian diffusion in the second stage. Close to the equilibrium swelling ratio, the swelling curve becomes nonmonotonic caused by a realignment of main chains of the hydrophilic phase in the third stage of swelling. Thus, by the unique combination of conventional swelling kinetics and solid-state NMR as well as PAL spectroscopies for investigating the aqueous swelling of the PVIm-l-PTHF amphiphilic polymeric conetwork, it was revealed that unexpected noncontinuous swelling occurs which is due to structural changes of the PVIm component in the conetwork in the course of this process.

Novel amphiphilic conetworks based on compatibilized NBR/SBR–montmorillonite nanovulcanizates as membranes for dehydrative pervaporation of water–butanol mixtures

“…In particular, the high solubility and thus swellability of the polystyrene and polybutadiene segments in the investigated NBR‐SBR conetworks contribute to the damaging effect on these membranes. These results are in good accordance with the swelling behavior of polymer conetworks such as amphiphilic bicomponent polymeric assemblies possessing exclusive swelling for the polymeric components in their good solvents .…”

Effect of aggregate size on liquid absorption characteristics of konjac glucomannan superabsorbent

“…Many efforts have been devoted on the influence factors of the water absorbency of superabsorbents in order to improve their water absorption properties such as the ultimate water absorption capacity and the rate of water absorption. These properties had relationships with monomer composition, degree of crosslinking, type of crosslinker, and polymerization process . On the other hand, physical factor, such as the particle size of superabsorbent was less discussed.…”

Novel Anti‐Biofouling Soft Contact Lens: l‐Cysteine Conjugated Amphiphilic Conetworks via RAFT and Thiol–Ene Click Chemistry

“…The cocontinuous microphase morphology in APCNs is achieved by skillful combination of the hydrophilic phase with the hydrophobic polydimethylsiloxane phase, which perfectly matches the need of extended-wear contact lenses. [5][6][7][8] Most APCNs are prepared by conventional free radical polymerization, [9][10][11][12] and the resultant conetworks generally possess bicontinuous microphase separation morphologies and the optical transparency is obtained when the microphase size is less than 100 nm. [1,[13][14][15] However, the APCN synthesis via free radical polymerization may be accompanied by some unavoidable imperfections, for example, although complete conversion of bismacromonomers is reported, [16] dangling chains may be formed by incomplete incorporation of the bifunctional cross-linker, which may lead to poor conformation regularity and structural defects in the conetworks.…”