Role of chain architecture in the solution phase assembly and thermoreversibility of aqueous PNIPAM/silyl methacrylate copolymers

Effect of Composition on the Thermo-Induced Aggregation of Poloxamer-Analogue Triblock Terpolymers

Thermoresponsive polymers hold great promise for biomedical applications due to their thermo-induced phase transitions. However, challenges including controlling transition temperatures, aggregate behavior, or complex synthesis, have limited their broader use. In this study, six ABC triblock terpolymers were synthesized via group transfer polymerization, targeting a molar mass of 8000 g/mol with varying compositions. The terpolymers consist of hydrophilic oligo(ethylene glycol) methyl ether methacrylate (average molar mass = 300 g/mol, OEGMA300), hydrophobic di(propylene glycol) methyl ether methacrylate (diPGMA), and less-hydrophilic di(ethylene glycol) methyl ether methacrylate (DEGMA). Systematic characterizations of properties related to thermo-induced aggregation, including cloud point temperature, aggregate morphology, and chain immobilization, identified a unique dual-stage phase transition in the terpolymer containing 45 wt % OEGMA300, 35 wt % diPGMA, and 20 wt % DEGMA. Instead of directly agglomerating into globular aggregates, this terpolymer transitioned from spherical micelles to vesicular species, offering valuable insights for the design of controllable and responsive polymer systems.

Cosolvent incorporation modulates the thermal and structural response of PNIPAM/silyl methacrylate copolymers

Polymers functionalized with inorganic silane groups have been used in wide-ranging applications due to the silane reactivity, which enables formation of covalently-crosslinked polymeric structures. Utilizing stimuli-responsive polymers in these hybrid systems can lead to smart and tunable behavior for sensing, drug delivery, and optical coatings. Previously, the thermoresponsive polymer poly(N-isopropyl acrylamide) (PNIPAM) functionalized with 3-(trimethoxysilyl)propyl methacrylate (TMA) demonstrated unique aqueous self-assembly and optical responses following temperature elevation. Here, we investigate how cosolvent addition, particularly ethanol and N,N-dimethyl formamide (DMF), impacts these transition temperatures, optical clouding, and structure formation in NIPAM/TMA copolymers. Versus purely aqueous systems, these solvent mixtures can introduce additional phase transitions and can alter the two-phase region boundaries based on temperature and solvent composition. Interestingly, TMA incorporation strongly alters phase boundaries in the water-rich regime for DMF-containing systems but not for ethanol-containing systems. Cosolvent species and content also alter the aggregation and assembly of NIPAM/TMA copolymers, but these effects depend on polymer architecture. For example, localizing the TMA towards one chain end in 'blocky' domains leads to formation of uniform micelles with narrow dispersities above the cloud point for certain solvent compositions. In contrast, polydisperse aggregates form in random copolymer and PNIPAM homopolymer solutions - the size of which depends on solvent composition. The resulting optical responses and thermoreversibility also depend strongly on cosolvent content and copolymer architecture. Cosolvent incorporation thus increases the versatility of inorganic-functionalized responsive polymers for diverse applications by providing a simple way to tune the structure size and optical response.

Preparation, Characterization, and Performance of a Modified Polyacrylamide-Sericite Gel

In this study, a modified chemical plugging agent is prepared with the aim to reduce the well moisture content and improve the efficiency of oilfield development. In comparison to other chemical plugging agents, the composite gels plugging agents have excellent blocking capacity and erosion resistance. In this study, optimal conditions for the preparation of plugging agents were explored. The results showed that the performance of polyacrylamide-sericite (PAM-sericite) gel improved at a polymerization temperature of 60 °C, a crosslinker concentration of 0.5%, an initiator concentration of 0.75%, an acrylamide concentration of 10.0%, and a sericite concentration of 10.0%. The characterization of PAM-sericite gel showed a certain fold-like shape with a smoother surface, indicating that the doped sericite makes the plugging agent more compact and firm. It was also found that the blocking ratio of the plugging agent can potentially reach 99.5% after the addition of sericite. Moreover, failure stress of the skeleton structure and the water swelling degree were increased by 63.5% and 51.2%, respectively. Additionally, long-term stability, temperature resistance, pressure resistance and pressure stability also showed improvement to varying degrees. It was concluded that this gel has better stability against different kinds of salt solutions and is not affected by particle size.