Synthesis of biocompatible and thermally sensitive poly(N‐vinylcaprolactam) nanogels via inverse miniemulsion polymerization: Effect of the surfactant concentration

Abstract

The goal of this study was to develop a new route to prepare thermally responsive polymer nanogels. Poly (N-vinylcaprolactam) nanogels were prepared via inverse miniemulsion polymerization (W/O) at 70 C using n-hexadecane as a nonpolar continuous phase, potassium persulfate as an initiator, and N,N 0 -methylenebisacrylamide as a crosslinker. Sorbitan monooleate (Span 80) was used as surfactant and its influence on the polymerization kinetics and on the colloidal characteristics of the nanogels were principally investigated. It was observed that the addition of a strong ''lipophobe'' is required to stabilize the resulting miniemulsion. The nanogels were characterized in terms of morphology, size, zeta potential, and thermoproperties using transmission electron microscopy and dynamic light scattering. It was observed that all the nanogels obtained collapsed when the lower critical solution temperature (LCST) was raised. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3932-3941, 2010

Poly(N-vinylcaprolactam), a comprehensive review on a thermoresponsive polymer becoming popular

“…A variety of techniques have been used to prepare PNVCL-based microgels/nanogels: dispersion polymerization [157][158][159], precipitation polymerization [160][161][162][163][164], and inverse micro-emulsion polymerization [165]. The preparation of thermo-responsive microgels in water requires that the polymerization be carried out at temperatures above its final LCST [156].…”

“…The most widely used crosslinker for micro/nanogels is BIS [47,152,162,165,172,173,175,176,178,179,182,[184][185][186][187]189,192,193,195,198,200]; while other crosslinkers were also used: N,Nbis(acryloyl) cystamine (BAC) [178], poly(ethylene glycol) diacrylate (PEGDA)…”

“…Surfactants are very important in the preparation of micro-/nanogels because they stabilize precursor particles and minimize their growth by aggregation. Widely used surfactants in the preparation of PNVCL micro/nanogels are sodium dodecyl sulphate [47,177,178,179,187,193,200,201,203], sodium lauryl sulphate (SLS) [175], Ndodecylpyridinium bromide (DPB) [202], N-cetyl-N,N,N-trimethylammonium bromide (CTAB) [42,193], hexadecyltrimethylammonium bromide (HDTAB) [195], and sorbitan monoleate [165]. Table 3 summarizes the reagents and reaction conditions used in different syntheses carried out in dispersed media to produce cross-linked /NVCL-based micro/nanogels.…”

Nanostructured Hydrogels

“…Poly(N-vinylcaprolactam) (PNVCL) is an example of a thermoresponsive and biocompatible polymer possessing a transition temperature or LCST close to physiological temperature (32À38 C) [121]. Its structure presents the nitrogen atom directly attached to the carbon, which does not allow the release of amide groups by hydrolysis; this characteristic makes this polymer suitable for biomedical applications.…”

Synthesis of nanostructured materials in inverse miniemulsions and their applications

“…1b, an inverse miniemulsion system is composed of a polar dispersed phase and a low-polarity continuous phase. 12 In addition, other surfactants with low HLB values, such as the SPAN series, sodium bis(2-ethylhexyl) sulfosuccinate, and amphiphilic polysaccharides, 13 may also be used in inverse miniemulsions. The surfactants, which may effectively provide colloidal stability in inverse miniemulsions have low HLB values.…”