{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,17]],"date-time":"2026-09-17T05:02:28Z","timestamp":1789621348483,"version":"build-2803163510"},"reference-count":45,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2026,9,10]],"date-time":"2026-09-10T00:00:00Z","timestamp":1788998400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Gels"],"abstract":"<jats:p>To mitigate clay hydration and wellbore instability during deepwater drilling, a pH\/temperature dual-responsive graft copolymer, hyperbranched polyethylenimine-g-poly(2-(dimethylamino)ethyl methacrylate) (HPEI-g-PDMAEMA), was designed and synthesized via free radical polymerization. Optimized synthesis at an HPEI\/DMAEMA mass ratio of 1:2 with 2.4% AIBN at 70 \u00b0C for 10 h yielded a grafting ratio of 35.2% and a molecular weight of 84.3 kDa. The copolymer exhibits a tunable lower critical solution temperature (LCST) of approximately 48 \u00b0C at pH 8, decreasing with increasing pH due to tertiary amine deprotonation. Zeta potential measurements confirm that the polymer retains a positive charge (+5 mV at pH 8) under weakly alkaline conditions, enabling strong electrostatic anchoring onto negatively charged clay surfaces. Above the LCST, dynamic light scattering reveals a sharp increase in hydrodynamic diameter from ~30 nm to &gt;200 nm, confirming a hydrophilic-to-hydrophobic transition of PDMAEMA segments that drives the formation of a hydrophobically associated gel barrier. This thermally triggered gelation is fully reversible, as evidenced by repeated heating\u2013cooling cycles with almost complete transmittance recovery. The gel barrier drastically reduces water uptake, with inhibition performance against clay swelling at 60 \u00b0C being 18.5 percentage points higher than that at 25 \u00b0C. Hot-rolling tests demonstrate that with only 1.5 wt% inhibitor, shale recovery reaches 94.1% at 150 \u00b0C (8.8 percentage points higher than unmodified HPEI) and remains above 60% even in 20 wt% CaCl2 or MgCl2 brines, highlighting exceptional resistance to divalent cations. Water contact angle on treated clay surfaces increases from 18.5\u00b0 to 52.6\u00b0, confirming effective surface hydrophobization. This work provides a molecular-level gel-engineering strategy where pH governs electrostatic anchoring and temperature triggers reversible hydrophobic gelation, enabling on-demand switching of clay wettability and hydration resistance under high-temperature, high-salinity conditions.<\/jats:p>","DOI":"10.3390\/gels12090830","type":"journal-article","created":{"date-parts":[[2026,9,10]],"date-time":"2026-09-10T15:54:19Z","timestamp":1789055659000},"page":"830","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["pH-\/Temperature-Triggered Gel Transition of Hyperbranched PEI-g-PDMAEMA as a Dual-Responsive Inhibitor for Clay Hydration Control"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8125-8518","authenticated-orcid":false,"given":"Ming","family":"Zhong","sequence":"first","affiliation":[{"name":"School of Energy and Resources, China University of Geosciences (Beijing), Beijing 100083, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yang","family":"Xiong","sequence":"additional","affiliation":[{"name":"School of Petroleum Engineering, Yangtze University, Wuhan 430100, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,10]]},"reference":[{"key":"ref_1","first-page":"999","article-title":"Investigating the synergistic effects of coconut coir fiber and xanthan gum on the rheology and filtration loss of water-based drilling fluids","volume":"44","author":"Verma","year":"2024","journal-title":"Pet. 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