Synthesis of N-vinylcaprolactam polymers in water-containing media

• Published in: Polymer (Guilford) Vol. 41; no. 17; pp. 6507 - 6518
• Main Authors: Lozinsky, V.I., Simenel, I.A., Kurskaya, E.A., Kulakova, V.K., Galaev, I.Yu, Mattiasson, B., Grinberg, V.Ya, Grinberg, N.V., Khokhlov, A.R.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-08-2000
• Subjects: Poly( N-vinylcaprolactam); Polymerization in aqueous media; Precipitation polymerization; Polymerization in aqueous media; Poly( N-vinylcaprolactam); Precipitation polymerization
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/S0032-3861(99)00844-7

Poly(
N-vinylcaprolactam) (PNVCl) is a polymer possessing a lower critical solution temperature (LCST) in aqueous solutions. To the best of our knowledge, we report the first synthesis of PNVCl in water-containing media, namely in DMSO/water mixtures with as low a DMSO concentration as 10% (v/v) using a pair persulphate/tertiary amine as the redox initiator. The polymerization was carried out in three ways: (i) in homogeneous system at 20°C (below LCST); (ii) as precipitation polymerization at 65°C (above LCST for the given DMSO/water compositions); and (iii) cryogenically at −20°C. The polymer MW distribution and tendency to segregate from solution and form a concentrated polymer phase depended on the solvent composition and polymerization temperature. PNVCl synthesized at 65°C had the largest fraction of high-molecular-weight polymer and the strongest tendency for temperature induced phase separation. Molecular-weight characteristics of the polymers obtained were evaluated with size-exclusion chromatography. Temperature-dependent solution behaviour of the samples was investigated with a thermoturbidimetric technique. Thermodynamic parameters of the temperature-induced phase separation were measured with high-sensitive differential scanning calorimetry. The synthetic methods developed are of interest for the preparation of
N-vinylcaprolactam copolymers with thermally unstable co-monomers or co-monomers insoluble in organic solvents, as well as for the synthesis of chemically cross-linked PNVCl hydrogels.