Synthesis,properties, and functions of thermosensitive copolymers having pyridyl and/or pyridinium groups

Thermosensitive copolymers with pyridyl and/or pyridinium groups were prepared by copolymerization of 4-vinylpyridine (4VP) and N-isopropylacrylamide (NIPAAm) followed by the reaction of 4VP–NIPAAm copolymers with benzyl chloride.The copolymer 4VP–NIPAAm was soluble in dilute HCl below 32 °C, but the quaternized 4VP–NIPAAm copolymer was soluble even in aqueous solutions of pH 6.5 below 28 °C. The thermosensitivity of both 4VP–NIPAAm and the quaternized 4VP–NIPAAm copolymer was observed. The quaternized 4VP–NIPAAm copolymer could adsorb food dyes dissolved in water and the copolymer–dye complexes became water-insoluble. The quaternized 4VP–NIPAAm copolymer also exhibited high antibacterial activity against bacteria such as Escherichia coli.     

Formation of thermosensitive copolymer beads having phosphinic acid groups and adsorption ability for metal ions

Hydrophilic thermosensitive copolymer beads having phosphinic acid groups were prepared by suspension copolymerization of acryloyloxypropyl n‐octylphosphinic acid (APPO), N‐isopropyl acrylamide (NIPAAm), and tetraethyleneglycol dimethacrylate (4G). The thermosensitivity and the adsorption ability of the copolymer beads for metal ions beads were studied. The APPO‐NIPAAm‐4G copolymer beads were obtained in a good yield by suspension copolymerization of monomers (APPO, NIPAAm, and 4G) dissolved in chloroform, in a saturated Na₂SO₄ aqueous solution in the presence of surfactant and MgCO₃. The APPO‐NIPAAm‐4G copolymer beads had higher adsorption ability for lanthanide metal ions (Eu³⁺, Sm³⁺, Nd³⁺, or La³⁺) than for main transition metal ions (Cu²⁺, Ni²⁺, or Co²⁺). Furthermore, it was also found that the APPO‐NIPAAm‐4G copolymer beads had selective adsorption ability between lanthanide metal ions, and the order of adsorption ability for lanthanide metal ions was as follows: Eu³⁺ > Sm³⁺ > Nd³⁺ > La³⁺. The selective adsorption for these metal ions from their mixed solutions was performed by both a batch method and a column method. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 449–460, 2006     

Synthesis of water‐soluble thermosensitive polymers having phosphonium groups from methacryloyloxyethyl trialkyl phosphonium chlorides–N‐isopropylacrylamide copolymers and their functions

Water‐soluble thermosensitive polymers having phosphonium groups were synthesized by the copolymerization of N‐isopropylacrylamide (NIPAAm) with methacryloyloxyethyl trialkyl phosphonium chlorides (METRs) having varying alkyl lengths. The relative viscosities of the copolymer solutions increased with increasing content of phosphonium groups in the copolymers and decreased with increasing chain length of alkyl chains in the phosphonium groups. However, the copolymers of METR with octyl groups in phosphonium groups (METO) and NIPAAm became water insoluble with increasing contents of METO moieties in the copolymers. The transmittance at 660 nm of the copolymer solutions above the lower critical solution temperature (LCST) decreased gradually with increasing temperature and decreased with increasing chain length of alkyl chains in the phosphonium groups. The transmittance at 660 nm of the copolymer solutions above the LCST was greatly affected by the addition of neutral salts such as KCl. The copolymers of METR with ethyl groups in phosphonium groups and NIPAAm and those of METR with butyl groups in phosphonium groups and NIPAAm had high flocculating abilities against bacterial suspensions. The METO–NIPAAm copolymer was found to have a high antibacterial activity. The flocculating ability and the antibacterial activity of the copolymers were affected by not only the content of phosphonium groups but also the alkyl chain length in the phosphonium groups in the copolymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 386–393, 2003     

Preparation of resins containing phenol derivatives from chloromethylstyrene-tetraethyleneglycol dimethacrylate copolymer beads and antibacterial activity of resins

Copolymer beads (RCCS-4G) with many chloromethyl groups were prepared by treating macroreticular chloromethylstyrene-tetraethyleneglycol dimethacrylate (4G) copolymer beads with chloromethylether. Copolymer beads (RAAS-4G) with benzylamino groups were prepared by treating RCCS-4G with potassium phthalimide. Then the copolymer beads containing phenol derivatives were prepared by treating RAAS-4G with p-hydroxybenzoic acid (pHBA), 2,4-dihydroxybenzoic acid (DHBA), and 3,4,5-trihydroxybenzoic acid (gallic acid, GA) in N,N-dimethylformamide. The antibacterial activity of the obtained resins was examined against Escherichia coli and Staphylococcus aureus. Resins containing phenolic hydroxy groups of 2.3–7.7 mequiv/g were obtained. Antibacterial activity of the resins containing various phenol derivatives against E. coli or S. aureus increased in the order of RAAS-4G-GA > RAAS-4G-DHBA > RAAS-4G-pHBA. The resins containing phenol derivatives exhibited higher antibacterial activity against E. coli than against S. aureus and high activity even against bacteria in NaCl solution. Scanning electron micrographs showed that high antibacterial activity was brought about by the phenolic hydroxyl groups in the resin. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1621–1630, 1997     

Preparation of thermosensitive and superabsorbent polymer hydrogels from trialkyl‐4‐vinylbenzyl phosphonium chloride‐N‐isopropylacrylamide‐N,N′‐methylenebisacrylamide copolymers and their properties

Thermosensitive and superabsorbent polymer hydrogels were synthesized by copolymerization of three kinds of tri‐n‐alkyl vinylbenzyl phosphonium chlorides (TRVB) with different lengths of alkyl chains, N‐isopropylacrylamide (NIPAAm), and N,N′‐methylenebisacrylamide (MBAAm). The water‐absorption ability and antibacterial activity of the hydrogels against Staphylococcus aureus (S. aureus) were investigated. The water content of TRVB–NIPAAm–MBAAm copolymers decreased with increasing temperature and increased with increasing phosphonium groups in the copolymers, while it decreased with increasing chain length of the alkyl groups in the phosphonium groups as well as with an increasing degree of crosslinking in the copolymers. The TRVB–NIPAAm–MBAAm copolymers with a higher TRVB content in the copolymers exhibited higher antibacterial activity against S. aureus, but decreased with increasing chain length of alkyl groups in phosphonium groups. The TRVB–NIPAAm–MBAAm copolymers exhibited the highest antibacterial activity at 30°C against S. aureus in deionized water. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 115–124, 2001     

Surface modification of electrospun chitosan nanofibrous mats for antibacterial activity

Chitosan (CS) blended with poly(ethylene oxide) (PEO) was electrospun into nanofibrous mats. The spinning solution of 6.7 : 0.3 (% w/v) of CS : PEO was dissolved in a 70 : 30 (v/v) trifluoroacetic acid/dichloromethane solution. The obtained fibers were smooth without beads on their surfaces and average diameter of the fiber was 272 ± 56 nm. N‐(2‐hydroxyl) propyl‐3‐trimethyl ammonium chitosan chloride (HTACC) and N‐benzyl‐N,N‐dimethyl chitosan iodide (QBzCS) were each prepared from the CS/PEO mats. They were identified by Fourier‐transform infrared and X‐ray photoelectron spectroscopy and degree of swelling in water. Both quaternized electrospun chitosan mats exhibited superior antibacterial activity to the unmodified electrospun CS/PEO against Staphylococcus aureus and Escherichia coli at short contact times. After 4 h of contact, the reduction of both bacterial strains by CS/PEO, HTACC, and QBzCS was equal at about 99–100%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40981.     

Thermosensitive and ampholytic hydrogels for salt solution

A series of N‐isopropylacrylamide/[[3‐(methacryloylamino)propyl]dimethy(3‐sulfopropyl)ammonium hydroxide] (NIPAAm/MPSA) copolymer hydrogels were prepared with various compositions. Swelling of the hydrogels in water, aqueous NaCl, KCl, CaCl₂, and MgCl₂ solutions was studied. NIPAAm/MPSA hydrogels have a higher degree of swelling in water and salt solutions than that of poly(N‐isopropylacrylamide) (PNIPAAm). Also, NIPAAm/MPSA hydrogels are more salt resistant when deswelling in salt solutions. For <7 mol % MPSA, the formed hydrogels retain both temperature reversibility and high swelling. A higher content of MPSA (>11 mol %) leads to better salt resistance but a decrease in thermosensitivity. The swelling of NIPAAm/MPSA hydrogel in 0.05M NaCl is non‐Fickian. In NaCl and KCl aqueous solutions, the zwitterionic hydrogels do not show obvious antipolyelectrolyte swelling behavior, whereas in divalent salt CaCl₂ and MgCl₂ solutions, the swelling ability of NIPAAm/MPSA hydrogels is enhanced at low salt concentration, then decreases with further increase in salt concentration. The lower critical solution temperatures of NIPAAm/MPSA hydrogels are also affected by concentrated salt solution. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2032–2037, 2003     

Functionalization of poly(4‐vinyl pyridine) grafted cellulose by quaternization reactions and a study on the properties of postquaternized copolymers

Graft copolymers of 4‐vinyl pyridine (4‐VP) synthesized by using simultaneous gamma irradiation method were further functionalized by post polymer quaternization reactions at N: of the pyridine ring of the graft copolymers. Using the optimum grafting conditions reported earlier for the grafting of 4‐VP onto extracted cellulose, graft copolymer was synthesized in bulk and was further functionalized by quaternization with hexyl bromide (C₆H₁₃Br), benzyl chloride (C₆H₅CH₂Cl), n‐butyl bromide (C₄H₉Br), and maleic anhydride (MAnh). The quaternized polymers were studied for treatment of hardness of water, antibacterial action, emulsification properties, metal ion uptake and stability toward thermal degradation, and enzymatic and alkaline hydrolysis to evaluate the suitability of these polymers in harsh chemical, microbial, and thermal environments. The functionalized polymers were also characterized for surface morphology (SEM), elemental analysis and FTIR for investigations of structural aspects, and to obtain evidence for quaternization. The functionalized copolymers exhibit a range of properties that can be used in many fields of water purification technologies including antibacterial agents and ion exchangers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2454–2464, 2004     

Thermoreversible hydrogels. VII. Synthesis and swelling behavior of poly(N‐isopropylacrylamide‐co‐3‐methyl‐1‐vinylimidazolium iodide) hydrogels

A series of N‐isopropylacrylamide/3‐methyl‐1‐vinylimidazolium iodide (NIPAAm/MVI) copolymer gels were prepared from the various molar ratios of NIPAAm, cationic monomer MVI, and N,N′‐methylene bisacrylamide (NMBA) in this study. The influence of the amount of MVI in the copolymer gels on the swelling behaviors was investigated in various aqueous saline solutions. Results showed that the swelling ratios (SRs) of copolymer gels were significantly greater than those of NIPAAm homopolymer gels, and the higher the MVI content, the higher the volume phase transition temperature. The SRs for the NIPAAm/MVI copolymer gels decreased with an increase of the salt concentration. In various saline solutions, results showed that the effect of divalent ions on the SR was greater than that of monovalent ions for these hydrogels. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3242–3253, 1999     

Synthesis and water absorbency of polyampholytic hydrogels with antibacterial activity

Amphoteric terpolymers of acrylic acid (AA), acrylamide (AM), and N,N′‐dimethyl‐N‐ethylmeth‐acryloxylethylammoniumbromide (DMAEA‐EB) with varied compositions P[AA‐AM‐(DMAEA‐EB)] were synthesized by inverse suspension polymerization. The components of P[AA‐AM‐(DMAEA‐EB)] were verified by FTIR spectroscopy. The water absorption ability and antibacterial activity of the copolymer against Escherichia coli(E. coli) and Staphylococcus hyicus(S. hyicus) suspended in sterilized physiological saline were investigated. The introduction of  N⁺R₄ may increase the water absorbency of P[AA‐AM‐(DMAEA‐EB)] in some degree because of the excellent hydrophilicity of  N⁺R₄. The AA‐AM‐(DMAEA‐EB) hydrogels exhibited high antibacterial activity against bacteria tested. The process of adsorption between live bacteria cells and resins was at least partially reversible. A peak of antibacterial efficiency existed with increasing contact time. The resin killed 96.6% E. coli organisms and 90.3% S. hyicus organisms, respectively, within 30 min of contact at dosage of 0.1g. The concentration of DMAEA‐EB has a special effect on the antibacterial activity of the polyampholytic hydrogels, which is different from polycation. It was observed that the antibacterial activity of the resin with 2 mol % of DMAEA‐EB is superior to the copolymers tested with other compositions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and swelling behavior of thermosensitive IPN hydrogels based on sodium acrylate and N‐isopropyl acrylamide by a two‐step method

A series of interpenetrating polymer network (IPN) hydrogels having higher swelling ratio (SR) and thermosensitivity were synthesized from sodium acrylate (SA) and N‐isopropyl acrylamide (NIPAAm) by a two‐step method. A series of the porous poly(sodium acrylate ‐co‐1‐vinyl–2‐pyrrolidone) [poly(SA‐co‐VP)], (SV), hydrogels were prepared from acrylic acid having 90% degree of neutralization and VP monomer in the first step. The second step is to immerse the SV dried gels into the NIPAAm solution containing initiator, accelerator, and crosslinker to absorb NIPAAm solution and then polymerized to form the poly(SA‐co‐VP)/poly(NIPAAm) IPN hydrogels (SVN). The effect of the different molar ratios of SA/VP and the content of NIPAAm on the swelling behavior and physical properties of the SVN hydrogels was investigated. Results showed that the SVN hydrogels displayed an obviously thermoreversible behavior when the temperature turns across the critical gel transition temperature (CGTT) of poly(NIPAAm) hydrogel. The pore diameter distributions inside the hydrogel also indicated that the pore sizes inside the SVN hydrogels were smaller than those inside the SV hydrogels. At the same time, the more proportion of SA was added into the hydrogel, the larger pore diameter of the SV hydrogel was formed. The results also showed that the SR decreased with an increase of the VP content in the SV hydrogel and more obviously decreased in the SVN hydrogels. The SVN networks also showed stronger shear moduli than SV hydrogels. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and antimicrobial activity of some cross‐linked copolymers with alkyl chains of various lengths

Amphoteric polymer hydrogels were prepared by the copolymerization of three kinds of N,N′‐dimethyl‐N‐alkylmethacryloxylethyl ammoniumbromide (DMAEA) with different lengths of alkyl chains (DMAEA‐RB) (R‐ehtyl/hexyl/dodecyl), acrylic acid (AA), and acrylamide (AM). The water content of the AA‐AM‐(DMAEA‐RB) terpolymers decreased with the increasing length of alkyl chains in quaternary ammonium group in the terpolymers and increased with the increasing molar ratio of DMAEA‐RB to 2 mol % and then decreased. Their antibacterial activities against Escherichia coli and Staphylococcus hyicus were investigated by a colony count method. It was found that the copolymer exhibited higher antibacterial activity with increasing chain length of alkyl groups in ammonium groups. For P[AA‐AM‐(DMAEA‐DB)], the DMAEA‐DB content is higher and contact time is longer, its antibacterial activity is better. However, when the contact time and quaternary ammonium content were above 30 min and 2%, respectively, the amount of live cells N(t) in a cell suspension increased in the presence of P[AA‐AM‐(DMAEA‐EB)] or P[AA‐AM‐(DMAEA‐HB)]. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Structure and antimicrobial activity relationship of quaternary N‐alkyl chitosan derivatives against some plant pathogens

In the present work, quaternary chitosans as water‐soluble compounds were prepared based on three‐step process. Schiff bases were firstly synthesized by the reaction between the amino groups of chitosan with aliphatic aldehydes followed by a reduction with sodium borohydride (NaBH₄) to form N‐(alkyl) chitosans. N,N,N‐(dimethyl alkyl) chitosans were then obtained by a reaction of chitosan containing N‐butyl, N‐pentyl, N‐hexyl, N‐heptyl, and N‐octyl substituents with methyl iodide. The compounds were characterized using IR and NMR spectroscopy. Subsequent experiments were conducted to test their antimicrobial activities against the most economic plant pathogenic bacteria of crown gall disease Agrobacterium tumefaciens, soft mold disease Erwinia carotovora, fungi of grey mold Botrytis cinerea, root rot disease Fusarium oxysporum, and damping off disease Pythium debaryanum. Quaternary chitosans enhanced the antibacterial activity and N,N,N‐(dimethyl pentyl) chitosan was the most active one with Minimum Inhibitory Concentration (MIC) of 750 and 1225 mg/L against A. tumefaciens and E. carotovora, respectively. All quaternized chitosans gave stronger antifungal activities than chitosan where N,N,N‐(dimethyl pentyl) chitosan and N,N,N‐(dimethyl octyl) chitosan were significantly the highest in mycelial growth inhibiation against B. cinerea (EC₅₀ = 908 and 383 mg/L, respectively), F. oxysporum (EC₅₀ = 871 and 812 mg/L, respectively), and P. debaryanum (EC₅₀ = 624 and 440 mg/L, respectively). In addition, spore germination of B. cinerea and F. oxysporum was significantly affected with the compounds at the tested concentrations and the inhibition activity was increased with an increase in the chain length of the alkyl substituent. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Miscibility and morphological properties of quaternized polysulfone blends with polystyrene and poly(4‐vinylpyridine)

Quaternized polysulfones were synthesized by the quaternization reaction of chloromethylated polysulfone with different tertiary amines −N,N‐dimethylethylamine (DMEA) and N,N‐dimethyloctylamine (DMOA), respectively. New blends from these quaternized polysulfones (PSF‐DMEA or PSF‐DMOA) with polystyrene (PS) or poly(4‐vinylpyridine) (P4VP) were prepared by the solution casting method. Pure quaternized polysulfones, in N,N‐dimethylformamide (DMF)/methanol (MeOH) and DMF/water solvent/nonsolvent mixtures, and their blends with PS and P4VP, as well, were investigated by shear viscometry and viscoelasticity, atomic force microscopy, differential scanning calorimetry, and surface properties. The results obtained revealed that the blends have good miscibility. Surface morphology is characterized by roughness and nodules formations, depending on the alkyl radical lengths, composition of the polymer mixtures, including specific electron‐donor or electron‐acceptor characteristics of polymers. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Synthesis,characterization, and antimicrobial properties of novel quaternary amine methacrylate copolymers

A novel amine methacrylate monomer trimethylolpropane trimethacrylate–piperazine–ethyleneglycol dimethacrylate (TMPTMA‐PPZ‐EGDMA) was synthesized by amination of trimethylolpropane trimethacrylate (TMPTMA) with excess of piperazine (PPZ) followed by reaction with ethyleneglycol dimethacrylate (EGDMA). Copolymerization of TMPTMA‐PPZ‐EGDMA with 2‐hydroxyethyl methacrylate (HEMA) was carried out by free radical polymerization using ammonium persulfate (APS) and N,N,N′,N′‐tetramethyl ethylenediamine (TEMED) as a redox initiator. The copolymers obtained were then quaternized with 1‐iodooctane. The monomers were characterized by FTIR and ¹H NMR spectral studies. The molecular weights and polydispersity values of the monomers were determined with gel permeation chromatography. Quaternized copolymers containing more than 20% amine methacrylate monomer showed microporosity in the range of 9.9–10.4 μm. The antibacterial activity of the quaternized copolymers against Escherichia coli and Staphylococcus aureus was studied using UV–vis spectrophotometer and scanning electron microscopy. Quaternized copolymers showed broad‐spectrum contact‐killing antibacterial properties without releasing any active agent as checked by iodide selective ion meter. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of superabsorbent polymer hydrogels from trialkyl‐4‐vinylbenzyl phosphonium chloride–acrylamide–methylenebisacrylamide terpolymers and their properties

Superabsorbent polymer gels were synthesized by terpolymerization of three kinds of tri‐n‐alkyl‐4‐vinylbenzyl phosphonium chloride (TRVB) with alkyl chains of different lengths, with acrylamide (AAm), and with N,N′‐methylenebisacrylamide (MBAAm). The water‐absorption ability and antibacterial activity of the gels against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were investigated. The water content of TRVB–AAm–MBAAm terpolymers increased with increasing phosphonium groups in the terpolymers, while the water content decreased with increasing chain length of alkyl groups in the phosphonium groups as well as an increasing degree of crosslinking in the terpolymers. The water content of the terpolymers was depressed by the addition of NaCl. The degree of effect of NaCl addition became higher as the chain length of alkyl groups in the phosphonium groups of the terpolymers became longer. The tri‐n‐octyl‐4‐vinylbenzyl phosphonium chlorides (TOVB)–AAm–MBAAm terpolymers exhibited high antibacterial activity against S. aureus and E. coli in deionized water. The antibacterial activity decreased in 0.9 wt % NaCl solution. The antibacterial activity of TOVB–AAm–MBAAm terpolymers with almost the same phosphonium content increased with the increasing swelling ratio of the terpolymers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1833–1844, 2000     

Graft copolymerization of N-isopropylacrylamide on styrene-butadiene-styrene block copolymer

Graft polymerization of N-isopropylacrylamide (NIPAAm) onto styrene-butadiene-styrene (SBS) block copolymer using benzoyl peroxide was studied to improve the water absorptivity and thermosensitivity of SBS. The influence of various grafting reaction factors on the conversion of NIPAAm and the grafting percentage of SBS-g-NIPAAm were also investigated in the study. The experimental results showed that the conversion of SBS-g-NIPAAm was enhanced as the monomers of NIPAAm were increased. The maximum conversion of SBS-g-NIPAAm was observed when the molar ratio of NIPAAm to butadiene was 1.25. In addition, increasing the reaction time enhanced the conversion of SBS-g-NIPAAm; the maximum grafting percentage was obtained with a 4-h reaction. The optimal concentration of the initiator was 3 × 10⁻⁴ mol/20 mL of toluene, and the grafting reaction occurred at over 65°C. The test results of the hydrophilicity of the grafted membranes showed that the hydrophilicity and thermosensitivity were significantly enhanced by grafting NIPAAm onto SBS. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2641–2650, 2001     

Two‐dimensional regular nanopatterning on block copolymer substrate having lamellar morphology using star‐hyperbranched nanospheres by electrostatic interaction

Hyperbranched polystyrenes (PS) were prepared by living radical photopolymerization of 4‐vinylbenzyl N,N‐diethyldithiocarbamate as an inimer under UV irradiation. The star‐hyperbranched copolymers were derived by grafting from surface N,N‐diethyldithiocarbamate groups of hyperbranched macroinitiator with t‐butyl methacrylate in the presence of N,N‐tetraethylthiuram disulfide. We obtained poly(methacrylic acid) star‐hyperbranched PS nanospheres by hydrolysis of poly(t‐butyl methacrylate)‐grafted chains. We established two‐dimensional (2D) regular nanopatterning by aligning continuously such nanospheres on poly(2‐vinylpyridine) (P2VP) lamellar layers of PS‐block‐P2VP diblock copolymer film. Electrostatic interaction between nanosphere surface having negative charges (? COOCs) and P2VP lamellar layer acted effectively for the 2D nanopattern formation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4206–4210, 2006     

Preparation,characterization, and thermal properties of polystyrene‐block‐quaternized poly(4‐vinylpyridine)/Montmorillonite nanocomposites

Polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) was synthesized by two steps of reversible addition‐fragmentation transfer (RAFT) polymerization of styrene (St) and 4‐vinylpyridine (4VP) successively. After P4VP block was quaternized with CH₃I, PS‐b‐quaternized P4VP/montmorillonite (PS‐b‐QP4VP/MMT) nanocomposites were prepared by cationic exchange reactions of quaternary ammonium ion in the PS‐b‐QP4VP with ions in MMT. The results obtained from X‐ray diffraction (XRD) and transmission electron microscopy (TEM) images demonstrate that the block copolymer/MMT nanocomposites are of intercalated and exfoliated structures, and also a small amount of silicates' layers remained in the original structure; differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) results show that the nanocomposites displayed higher glass transition temperature (T_g) and higher thermal stability than that of the corresponding copolymers. The blending of PS‐b‐QP4VP/MMT with commercial PS makes MMT to be further separated, and the MMT was homogeneously dispersed in the polymer matrix. The enhancement of thermal stability of PS/PS‐b‐QP4VP/MMT is about 20°C in comparison with commercial PS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1950–1958, 2006     

Thermoreversible hydrogels XIII: Synthesis and swelling behaviors of [N-isopropylacrylamide-co-sodium 2-acrylamido-2-methylpropyl sulfonate-co-N,N-dimethyl(acrylamido propyl) ammonium propane sulfonate] copolymeric hydrogels

A series of copolymeric hydrogels were prepared from various molar ratios of N-isopropylacrylamide (NIPAAm), sodium-2-acrylamido-2-methylpropyl sulfonate (NaAMPS) and N,N′-dimethyl(acrylamido propyl) ammonium propane sulfonate (DMAAPS). The swelling behaviors of these copolymeric hydrogels were investigated in various saline solutions. The result showed that the phase transition temperatures of these gels changed insignificantly, and the thermosensitivity, in contrast, diminished. In addition, the copolymer gels exhibited polyelectrolytic behavior under lower salt concentration (10⁻⁵∼10⁻¹ M), exhibited a nonionic gel (like NIPAAm) behavior at the salt concentration from 0.1 to 0.4 M, and showed an antipolyelectrolytic behavior (polyzwitterionic effect) at a salt concentration over 0.4 M. Finally, the presented coplymeric gels are investigated for use in drug release application.