Physical Gelation of Amphiphilic Poly(N‐isopropylacrylamide): Influence of the Hydrophobic Groups

Abstract

The self‐assembling properties of hydrophobically modified (N‐isopropylacrylamide) have been investigated by dynamic light scattering and rheological measurements. Size of the globules and transmission of the solutions vary strongly in the same range of temperature. The presence of hydrophobic groups leads to contraction of the globules' size compared to poly(N‐isopropylacrylamide) (PNIPAM). The viscoelastic properties of the samples in aqueous solution have been investigated as a function of copolymer concentration, structure of the hydrophobic group (dodecyl or adamantyl group), substitution level (1–5%) and over a temperature range covering the lower critical solution temperature (LCST). At high concentration and high level of adamantyl substitution, gelation is observed several degrees before the phase transition. A physical network is formed due to the strong hydrophobic interactions, and this physical gel undergoes phase transition without macroscopic phase separation.magnified image

Copolymers based on azidopentyl-2-oxazoline: Synthesis, characterization and LCST behavior

“…Several synthetic polymers that respond to this criteria are known from literature: poly(methyl vinyl ether) [7,8], polyethers [9][10][11][12][13][14], poly(N-vinyl caprolactam) [15], poly [2-(dimethylamino)ethyl methacrylate] [16,17] or poly(N-isopropylacrylamide) (PNIPAM) [18][19][20][21]. PNIPAM is the most studied thermosensitive water-soluble polymers with a LCST of 32°C [18].…”

Synthesis of 3‐(tert‐Butoxycarbonylmethyl)‐N‐vinyl‐2‐caprolactam and Homologous Copolymerization Toward Biocompatible Carboxylated Poly(N‐vinyl‐2‐caprolactam) Responsive to pH and Temperature

“…Our results correlated well with the study by Wintgens and Amiel, where thermoresponsive PNIPAM was hydrophobically modified with bulky adamantly group. It was observed that sharp transitions occurred in the case of PNIPAMs with low substitution levels (1.4%), in contrast to the broader transitions for PNIPAMs with high substitution levels (4.5%) …”

In vitro–in vivo evaluation of hyaluronic acid-based amphiphilic copolymers for tumour targeted delivery: the role of hydrophobic groups

“…Studies have shown that hydrophobic groups can increase the solubility of hydrophobic drugs and the stability of the micelles. 4,5 It also has been reported that the hydrophobic groups can affected the rheological properties of the carrier 6 and the antibacterial activity. 7 Even more the length of hydrophobic groups displayed the decisive effect on the gelation behaviour.…”