Temperature-responsive self-assembly of charged and uncharged hydroxyethylcellulose-graft-poly(N-isopropylacrylamide) copolymer in aqueous solution

Abstract

Temperature-induced interchain association and contraction of species in aqueous solutions of charged (MHEC(−)-g-PNIPAAM) and uncharged (MHEC-g-PNIPAAM) modified hydroxyethylcellulose-graft-poly(N-isopropylacrylamide) copolymer have been studied with the aid of turbidimetry and dynamic light scattering (DLS). It was shown that by attaching PNIPAAM chains to the backbone of a hydrophilic cellulose derivative, a strongly temperature-responsive copolymer could be prepared. The results show an intriguing interplay between interchain association and contraction of the multichain species. The transition zone for compression is narrow, and the compaction effect is promoted by a low polymer concentration and charges on the polymer moieties. The findings from DLS revealed two populations of species, namely molecularly dispersed molecules or small clusters and interchain complexes, which exhibit temperature-induced collapse. The magnitude of the cluster contraction can be modulated by changing the polymer concentration and charge density of the copolymer.

Characterization of temperature induced changes in liposomes coated with poly( N -isopropylacrylamide- co -methacrylic acid)

“…Interestingly, when the temperature was increased the thickness of the polymer coating exhibited a maximum. This is contributed to the competition between inter-and intramolecular interactions between the PNIPAAM chains [51,62], causing both multilayer formation and a more compact polymer coating. Unlike what is observed for some liposomes coated with hydrophobically modified PNIPAAM [12], the electrostatic deposition does not cause the liposomes to fragment into smaller entities.…”

“…The thickness of the polymer coating is dependent on the number of adsorbed polymer chains and on the compactness of the adsorbed layer. Elevated temperatures enhances both inter-and intramolecular interactions between the PNIPAAM chains [51,62]. Accordingly, the intermolecular attractive forces will promote multilayer formation of polymer onto the liposomes (resulting in larger sizes), while intramolecular interactions will cause the adsorbed layer to contract (reducing the size).…”

The Synthesis of a Novel Cellulose Physical Gel

“…In light of material application concerns, cellulose gels have received increasing attention in recent years [22,23]. Cellulose supramolecular materials linked by noncovalent bondshave attracted much more attention and have been widely studied [24]; their responsiveness to the external environment [25], such as temperature [26], pH [27], and medicine (drug release carriers) [28] have been of particular interest.…”

Amphiphilic Molecular Brushes with Regular Polydimethylsiloxane Backbone and Poly-2-isopropyl-2-oxazoline Side Chains. 2. Self-Organization in Aqueous Solutions on Heating

“…At low concentrations ( c < 0.001 g·cm −3 ), the temperature boundaries of phase separation increase with dilution. This is typical for solutions of thermosensitive polymers in the diluted region [ 83 , 84 , 85 , 86 , 87 , 88 ]. For Sample 1, the widening of the phase separation interval T 2 − T 1 is also detected with dilution.…”