PNIPAM-b-PDMAEA double stimuli responsive copolymers: Effects of composition, end groups and chemical modification on solution self-assembly

Influence of Nanoaggregation Routes on the Structure and Thermal Behavior of Multiple-Stimuli-Responsive Micelles from Block Copolymers of Oligo(ethylene glycol) Methacrylate and the Weak Acid [2-(Hydroxyimino)aldehyde]butyl Methacrylate

In this work, we compare nanoaggregation driven by pH-induced micellization (PIM) and by the standard solvent displacement (SD) method on a series of pH-, light-, and thermosensitive amphiphilic block copolymers. Specifically, we investigate poly(HIABMA)-b-poly(OEGMA) and poly(HIABMA)-b-poly(DEGMA-r-OEGMA), where HIABMA = [(hydroxyimino)aldehyde]butyl methacrylate, OEGMA = oligo(ethylene glycol)methyl ether methacrylate, and DEGMA = di(ethylene glycol)methyl ether methacrylate. The weakly acidic HIA group (pK_a ≈ 8) imparts stability to micelles at neutral pH, unlike most of the pH-responsive copolymers investigated in the literature. With SD, only some of our copolymers yield polymeric micelles (34-59 nm), and their thermoresponsivity is either poor or altogether absent. In contrast, PIM affords thermoresponsive, smaller micelles (down to 24 nm), regardless of the polymer composition. In some cases, cloud points are remarkably well defined and exhibit limited hysteresis. By combining turbidimetric, dyamic light scattering, and small-angle X-ray scattering measurements, we show that SD yields loose micelles with POEGMA segments partly involved in the formation of the hydrophobic core, whereas PIM yields more compact core-shell micelles with a well-defined PHIABMA core. We conclude that pH-based nanoaggregation provides advantages over block-selective solvation to obtain compact micelles exhibiting well-defined responses to external stimuli.

Poly(N-isopropylacrylamide)-Based Hydrogels for Biomedical Applications: A Review of the State-of-the-Art

A prominent research topic in contemporary advanced functional materials science is the production of smart materials based on polymers that may independently adjust their physical and/or chemical characteristics when subjected to external stimuli. Smart hydrogels based on poly(N-isopropylacrylamide) (PNIPAM) demonstrate distinct thermoresponsive features close to a lower critical solution temperature (LCST) that enhance their capability in various biomedical applications such as drug delivery, tissue engineering, and wound dressings. Nevertheless, they have intrinsic shortcomings such as poor mechanical properties, limited loading capacity of actives, and poor biodegradability. Formulation of PNIPAM with diverse functional constituents to develop hydrogel composites is an efficient scheme to overcome these defects, which can significantly help for practicable application. This review reports on the latest developments in functional PNIPAM-based smart hydrogels for various biomedical applications. The first section describes the properties of PNIPAM-based hydrogels, followed by potential applications in diverse fields. Ultimately, this review summarizes the challenges and opportunities in this emerging area of research and development concerning this fascinating polymer-based system deep-rooted in chemistry and material science.

Precision synthesis for well-defined linear and/or architecturally controlled thermoresponsive poly(N-substituted acrylamide)s

We describe the progress in precision polymerizations of specific kinds of N-alkylacrylamides and N,N-dialkylacrylamides to produce polymers showing thermoresponsive properties in aqueous media, which representatively include the reversible-deactivation radical polymerizations...

Reduction-responsive double hydrophilic block copolymer nano-capsule synthesized via RCMP-PISA

Double hydrophilic block copolymer vesicles synthesized via RCMP-PISA are degradable under a reductive conditions.

Application of the liquid-liquid dispersed microextraction based on phase transition behavior of temperature sensitive polymer to rapidly detect 5 BPs in food packaging

In this paper, temperature sensitive polymer p(MAH-β-CD-co-NIPAM) was used as extraction in DLLME, because its phase transition behavior can be observed at room temperature due to Hofmeister and non-co-solvent effect. The whole pretreatment process is simple and fast, and the extraction process did not require dispersant to assist dispersion and centrifugation to collect the adsorbent. A new analytical method based on DLLME coupled with HPLC-UV was developed to detect five types of BPs in milk and take-out packaging. The limits of detection ranged from 0.44 to 1.60 ng mL^-1 (S/N = 3). The relative recoveries of 5 BPs in food packaging were in the range of 91.08-108.04%.