Swelling of thin films. I. Acrylamide–N‐isopropylacrylamide copolymers in water

Abstract

The swelling curves of 6μ films of low conversion homopolymers and copolymers of acrylamide (AM) and N‐isopropylacrylamide (NIPAM) were obtained in water by an optical microscope technique. Poly(AM) swelled appreciably faster than poly(NIPAM) but there was no apparent correlation between overall swelling rate and copolymer composition. A 57/43 (mole %) AM–NIPAM copolymer swelled fastest. Sequence distribution calculations indicated that its backbone structure tended toward comonomer alternation, which might reduce the extent of hydrogen bonding in the film. The amount of water sorbed during swelling, as approximated from increasing film thickness, was proportional to the square root of time and agreed well with previous work in the literature. Homopolymer films from runs of ca. 50% conversion consistently swelled slower than their low conversion counterparts, probably due to branching and increased entanglements. Heating also promoted slower film swelling due to a tightening of the film structure and/or a low degree of imidization. Monomer reactivity ratios and Alfrey‐Price Q and e values for NIPAM were calculated. Cloud points of 5% aqueous solutions of the copolymers were measured and found to decrease with increasing NIPAM content.

The surface tension of aqueous poly(N-isopropylacrylamide-co-acrylamide)

“…This observation is consistent with the work of Chiklis and Grasshoff, which showed that AM is more reactive than NIPAM. 3 A more detailed analysis of copolymer microstructure is given in the discussion section.…”

“…Pendant drops were formed on the tip of a Teflon capillary with an outside diameter of 0.1 inch and inside diameter of 0.076 inch (Chromatographic Specialties Inc.). The pendant drop was enclosed in a sealed quartz cuvette (Hellma 330984, 10 ϫ 10 ϫ 30 mm, 3 Hellma), which was mounted in a Model 100-07 environmental chamber (Ramé Hart Inc.). The temperature control was Ϯ0.1°C.…”

“…1 Copolymers of NIPAM and acrylamide are also temperature sensitive [2][3][4] and the copolymers have been evaluated for applications in enhanced/tertiary oil recovery, [5][6][7][8] optical "switching" devices, 9 biotechnology, 10 -14 drag reduction, 15,16 membrane technology, 17 and chromatography. 18 Since acrylamide (AM) is more hydrophilic than NIPAM, the LCST of the copolymers increases with acrylamide content.…”

Thermoassociative graft copolymers based on poly(N-isopropylacrylamide): Relation between the chemical structure and the rheological properties

“…As for the distribution of the different units inside the copolymer chains, we can only find information for the NIPA-AAm copolymerization. In that case, Chiklis and co-workers 17) have reported the following reactivity ratios: r NIPA = 0.5 and r AAm = 1.0. These values indicate that the heterogenity of the cotelomers, due to the composition drift with conversion, is rather low.…”

Temperature-dependent adsorption/desorption behavior of lower critical solution temperature (LCST) polymers on various substrates

“…It is known that some water soluble polymers exhibit a lower critical solution temperature (LCST) in aqueous solution [1][2][3][4][5][6][7]. For example, poly-N-isopropylacrylamide (poly(NIPAAm)) has an LCST around 32°C [2][3][4][5].…”