Synthesis and Aqueous Solution Properties of Novel Thermoresponsive Graft Copolymers Based on a Carboxymethylcellulose Backbone

Abstract

The synthesis of thermoresponsive graft copolymers based on a carboxymethylcellulose (CMC) backbone is reported. Thermal responsive properties are introduced by grafting the CMC sample with amino-terminated poly(N-isopropylacrylamide) (PNIPAM) side chains of a relatively low molecular weight. Turbidity measurements in dilute copolymer solutions showed that, due to the hydrophilic CMC backbone, macroscopic phase separation by increasing temperature above the lower critical solution temperature (LCST) of PNIPAM is not allowed for pH ≥ 3. Pyrene fluorescence probing studies in aqueous solutions revealed the formation of hydrophobic microdomains above the LCST of PNIPAM. In semidilute solution these microdomains interconnect the polymer chains, leading to the thermally induced formation of a physical network. The macroscopic result is the observation in semidilute solutions of a pronounced thermally induced viscosity enhancement. This thermothickening phenomenon is almost irrespective of pH, and it remains very important even at pH values as low as 3.

Synthesis and gelation properties of poly(2-alkyl-2-oxazoline) based thermo-gels

“…below the T cp ), an important consideration as carboxymethylcellulose is insoluble in other less polar solvents. As previously reported for similar reactions 9,19 the efficiency of the coupling reaction proved to be poor, as indicated by the small percentage of nitrogen in the elemental analysis. This arises from: slowing of the reaction at low temperatures; the poor stability of the coupling agent, which is only stable for a short period of time in water; and the effect of pH limiting the efficiency of the coupling activation of the carboxylic acids which proceeds best at ca.…”

“…However, 2-isopropyl-2-oxazoline and 2-n-butyl-2-oxazoline have different reactivity and so a gradient polymer would be expected, in which the butyl oxazoline is the more reactive component 17 . A cross-coupling reaction then allowed the poly(2-alkyl-2-oxazoline)s to be grafted onto the CMC backbone under mild conditions in water as depicted in Figure 3, using a modified procedure based on previous work in the literature 9,19 . This allowed the reaction to proceed under cold, aqueous conditions (i.e.…”

Enzymatic degradation of thermoresponsive poly(N‐isopropylacrylamide) grafted to carboxymethylcellulose copolymers

“…The synthesis of the CMC-g-PNIPAM27 and CMCg-PNIPAM47 copolymers has been described elsewhere, 2 the numbers 27 and 47 indicating the weight percentage composition of the graft copolymers in N-isopropylacrylamide units.…”

“…Graft copolymers synthesized either by grafting of a macromolecular chain onto a polysaccharide backbone 1,2 or by polymerization of the appropriate monomers in the presence of a polysaccharide 3,4 have received considerable attention during the past few years due to their wide applications in various fields such as papermaking, textiles, petroleum washing, environmental protection, or biomedical applications. 5,6 Moreover, the synthesis of materials that continue to have functionality while in service but degrade after use is a rather novel concept in the development of new materials.…”

Stimuli‐Responsive Hydrogels Based on Polysaccharides Incorporated with Thermo‐Responsive Polymers as Novel Biomaterials

“…In a similar way, Bokias et al grafted carboxymethylcellulose (CMC) onto amine-terminated PNIPAAm. [84] The grafted CMC formed hydrophobic microdomains at above 32 8C. These microdomains between PNIPAAm side chains of the graft copolymer form a thermally induced physical network in semi-dilute solution, leading to pronounced thermo-thickening properties.…”