The　poly(methylacrylic　acid)　modified　by　silane　[poly(methylacrylic　acid-co-vinyl　triethoxylsilane)　(PMAA)]　was　prepared　via　free-radical　polymerization　with　different　mass　ratios　of　methylacrylic　acid　to　vinyl　triethoxylsilane　(VTES).　The　swelling　performance　of　the　prepared　PMAA　in　different　solutions　with　various　pH　values,　salt　species　(NaCl　and　CaCl2),　and　concentrations　was　investigated　in　detail.　The　results　indicated　that　the　introduction　of　silane　boosted　the　stability　of　the　obtained　PMAA　in　aqueous　solutions　in　the　presence　of　an　increased　quantity　of　VTES　additive.　Meanwhile,　the　different　swelling　ratios　of　PMAA　in　various　pH　solutions　showed　a　high　pH　responsivity.　In　addition,　we　found　that　when　the　PMAA　underwent　a　number　of　swelling-deswelling　cycles,　it　demonstrated　the　good　reversibility　properties　when　the　pH　value　of　the　swelling　medium　was　changed　from　9.0　to　1.4.　Moreover,　the　swelling　mechanism　of　PMAA　in　different　solutions　with　different　pH　values　was　investigated.　(c)　2014　Wiley　Periodicals,　Inc.　J.　Appl.　Polym.　Sci.　2014,　131,　40403.