Thermoresponsive and biocompatible poly(vinyl alcohol)‐graft‐poly(N,N‐diethylacrylamide) copolymer: Microwave‐assisted synthesis,characterization, and swelling behavior

Novel thermoresponsive poly(vinyl alcohol)‐graft‐poly(N,N‐diethylacrylamide) (PVA‐g‐PDEAAm) copolymers were prepared by microwave‐assisted graft copolymerization using a potassium persulfate/N,N,N′,N′‐tetramethylethylenediamine (KPS/TEMED) initiator system. The structures of PVA‐g‐PDEAAm copolymers were characterized by ¹H‐NMR, Fourier transform infrared spectroscopy, differential scanning calorimetry/thermogravimetric analysis, gel permeation chromatography, X‐ray diffraction, and scanning electron microscopy. The effects of various process parameters on grafting were systematically studied: microwave power, KPS, monomer and PVA concentrations, and ultraviolet irradiation. Under optimal conditions, the maximum grafting percent and graft efficiency were 101% and 93%, respectively. Furthermore, a lower critical temperature of copolymers was measured in the range 29–31 °C by ultraviolet spectroscopy. The swelling behavior of graft membranes was carried out at various temperatures, and the results showed that the swelling behavior of membranes was dependent on the temperature. In vitro cell culture studies using L929 fibroblast cells confirmed cell compatibility with the PVA‐g‐PDEAAm copolymer and its membrane, making them an attractive candidate for drug delivery systems. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45969.     

A study on solution properties of poly(N,N‐diethylacrylamide‐co‐acrylic acid)

Poly(N,N‐diethylacrylamide) (PDEA), poly(acrylic acid) (PAA), and a series of (N,N‐diethylacrylamide‐co‐acrylic acid) (DEA‐AA) random copolymers were synthesized by the method of radical polymerization. The measurement of turbidity showed that the phase behaviors of the brine solutions of the copolymers changed dramatically with the mole fraction of DEA (x) in these copolymers. Copolymers cop6 (x = 0.06) and cop11 (x = 0.11) in which acrylic acid content was higher presented the upper critical solution temperature (UCST) phase behaviors similar to PAA. Copolymer cop27 (x = 0.27) presented the lower critical solution temperature (LCST) behavior similar to PDEA. While copolymer cop18 (x = 0.18) in which acrylic acid content was moderate presented both UCST and LCST behaviors. The solution properties of the polymers were investigated by measurements of viscosity, fluorescence, and pH. It is reasonable to suggest that the sharp change of the phase behavior may be attributed to the interaction between acrylamide group and carboxylic group in the (DEA‐AA) copolymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Phase behavior of temperature‐ and pH‐sensitive poly(acrylic acid‐g‐N‐isopropylacrylamide) in dilute aqueous solution

Several different composition temperature‐ and pH‐sensitive poly(acrylic acid‐g‐N‐isopropylacrylamide) (P(AA‐g‐NIPAM)) graft copolymers were synthesized by free‐radical copolymerization utilizing macromonomer technique. The phase behavior and conformation change of P(AA‐g‐NIPAM) in aqueous solutions were investigated by UV–vis transmittance measurements, fluorescence probe, and fluorescence quenching techniques. The results demonstrate that the P(AA‐g‐NIPAM) copolymers have temperature‐ and pH‐sensitivities, and these different composition graft copolymers have different lower critical solution temperature (LCST) and critical phase transition pH values. The LCST of graft copolymer decreases with increasing PNIPAM content, and the critical phase transition pH value increases with increasing Poly(N‐isopropylacrylamide) (PNIPAM) content. At room temperature (20°C), different composition of P(AA‐g‐NIPAM) graft copolymers in dilute aqueous solutions (0.001 wt %) have a loose conformation, and there is no hydrophobic microdomain formation within researching pH range (pH 3 ～ 10). In addition, for the P(AA‐g‐NIPAM) aqueous solutions, transition from coil to globular is an incomplete reversible process in heating and cooling cycles. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

pH and thermo‐responsive poly(N‐isopropylacrylamide) copolymer grafted to poly(ethylene glycol)

pH and thermo‐responsive graft copolymers are reported where thermo‐responsive poly(N‐isopropylacrylamide) [poly(NIPAAm), poly A ], poly(N‐isopropylacrylamide‐co‐2‐(diethylamino) ethyl methacrylate) [poly(NIPAAm‐co‐DEA), poly B ], and poly(N‐isopropylacrylamide‐co‐methacrylic acid) [poly(NIPAAm‐co‐MAA), poly C ] have been installed to benzaldehyde grafted polyethylene glycol (PEG) back bone following introducing a pH responsive benzoic‐imine bond. All the prepared graft copolymers for PEG‐g‐poly(NIPAAm) [ P‐N1 ], PEG‐g‐poly(NIPAAm‐co‐DEA) [ P‐N2 ], and PEG‐g‐poly(NIPAAm‐co‐MAA) [ P‐N3 ] were characterized by ¹H‐NMR to assure the successful synthesis of the expected polymers. Molecular weight of all synthesized polymers was evaluated following gel permeation chromatography. The lower critical solution temperature of graft copolymers varied significantly when grafted to benzaldehyde containing PEG and after further functionalization of copolymer based poly(NIPAAm). The contact angle experiment showed the changes in hydrophilic/hydrophobic behavior when the polymers were exposed to different pH and temperature. Particle size measurement investigation by dynamic light scattering was performed to rectify thermo and pH responsiveness of all prepared polymers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and characterization of alginate‐g‐vinyl sulfonic acid with a potassium peroxydiphosphate/thiourea system

Alginate‐g‐vinyl sulfonic acid graft copolymer was synthesized through the graft copolymerization of vinyl sulfonic acid (VSA) onto alginate with an efficient system, i.e., potassium peroxydiphosphate (PDP)/thiourea in an aqueous medium. The effects of the concentration of thiourea, PDP, hydrogen ion, alginate, and VSA along with the time and temperature on the graft copolymerization were studied by the determination of the grafting parameters (grafting ratio, add‐on, conversion, grafting efficiency, and homopolymer). The synthesized graft copolymer was characterized by FTIR analysis. Thermogravimetric analysis showed that the alginate‐g‐vinyl sulfonic acid is thermally more stable than alginate. Water swelling capacity, metal ion sorption, flocculation, and resistance to biodegradability studies of synthesized graft copolymer have been performed with respect to the parent polymer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Bioengineering functional copolymers: V. Synthesis,LCST, and thermal behavior of poly(N‐isopropyl acrylamide‐co‐p‐vinylphenylboronic acid)

New boron‐containing stimuli‐responsive (pH‐ and temperature‐sensitive) copolymers were synthesized and characterized. Structure and composition of copolymers were determined by FTIR and ¹H‐NMR spectroscopy, and elemental analysis and titration (N and B contents for NIPA and VPBA unit, respectively). By DSC and XRD measurements, it is established that the synthesized copolymers have a semicrystalline structure due to formation of intra‐ and/or intermolecular H‐bonded supramolecular architecture. The copolymer composition–structure–property relationship indicates semicrystalline structure of copolymers with different compositions, degrees of crystallinity, and thermal and stimuli‐responsive behaviors depends on the content of boron‐containing monomer linkage. Results of DSC, DTA, and TGA analyses indicated that copolymers have T_g and T_m and high thermal stability. These water‐soluble and temperature‐ and pH‐sensitive amphiphilic copolymers can be used as polymeric carries for delivery of biological entities for diverse biomedical use, including boron neutron capture therapy. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 573–582, 2005     

Synthesis of pH‐ and temperature‐responsive chitosan‐graft‐poly[2‐(N,N‐dimethylamino) ethyl methacrylate] copolymer and gold nanoparticle stabilization by its micelles

Novel pH‐ and temperature‐responsive chitosan‐graft‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate] (chitosan‐g‐PDMAEMA) copolymers were successfully synthesized by homogeneous atom transfer radical polymerization (ATRP) under mild conditions. Chitosan macroinitiator was prepared by phthaloylation of amino groups of chitosan and subsequent acylation of hydroxyl groups of chitosan with 2‐bromoisobutyryl bromide. The copolymers were obtained by ATRP of 2‐(N,N‐dimethylamino)ethyl methacrylate and they can self‐assemble into stable micelles in water. Hybrid micelles with a PDMAEMA corona incorporating gold nanoparticles (Au NPs) were prepared in situ via the reduction of HAuCl₄ with NaBH₄. The pH and temperature responses of the copolymer micelles and hybrid micelles were characterized using UV‐visible spectroscopy and dynamic laser light scattering. The morphology of the micelles was observed using transmission electron microscopy and atomic force microscopy. The PDMAEMA corona of the micelles acts as the ‘nanoreactor’ and the ‘anchor’ for the in situ formation and stabilization of Au NPs. Therefore, the spatial distribution of Au NPs within the micelles can be tuned by varying the temperature and pH value. Copyright © 2010 Society of Chemical Industry     

Synthesis and characterization of temperature‐responsive copolymers based on N‐vinylcaprolactam and their grafting on fibres

BACKGROUND: Responsive materials are able to respond reversibly to an environmental stimulus. When the stimulus is temperature in the physiological range, the responsive material is particularly interesting for textile applications. We describe here the synthesis and characterization of reactive temperature‐responsive copolymers and their subsequent grafting on cotton fabrics. RESULTS: Copolymers of N‐vinylcaprolactam and various reactive monomers were synthesized via free radical polymerization in solution. The copolymers were characterized in terms of chemical structure, molecular weight and temperature‐responsive properties. The copolymer of N‐vinylcaprolactam and methacrylic acid (11 or 22 wt%) and the hydrolysed copolymer of N‐vinylcaprolactam and acryloyl chloride were found to be temperature responsive. They were subsequently grafted on cotton fabrics. The grafting was studied using X‐ray photoelectron spectroscopy and scanning electron microscopy measurements and was found to be effective. Finally, the modified cotton fabrics were found to exhibit temperature‐responsive water regain and water vapour transmission rates. CONCLUSION: Temperature‐responsive copolymers were synthesized, characterized and successfully grafted on cotton fabrics, yielding responsive fabrics. Such fabrics can hence be used to modulate the skin microclimate under textiles. Copyright © 2009 Society of Chemical Industry     

Poly(ε‐caprolactone)‐graft‐poly(N‐isopropylacrylamide) amphiphilic copolymers prepared by a combination of ring‐opening polymerization and atom transfer radical polymerization: Synthesis,self‐assembly,and thermoresponsive property

Thermoresponsive graft copolymers of ε‐caprolactone and N‐isopropylacrylamide were synthesized by a combination of ring‐opening polymerization and the sequential atom transfer radical polymerization (ATRP). The copolymer composition, chemical structure, and the self‐assembled structure were characterized. The graft length and density of the copolymers were well controlled by varying the feed ratio of monomer to initiator and the fraction of chlorides along PCL backbone, which is acting as the macroinitiator for ATRP. In aqueous solution, PCL‐g‐PNIPAAm can assemble into the spherical micelles which comprise of the biodegradable hydrophobic PCL core and thermoresponsive hydrophilic PNIPAAm corona. The critical micelle concentrations of PCL‐g‐PNIPAAm were determined under the range of 6.4–23.4 mg/L, which increases with the PNIPAAm content increasing. The mean hydrodynamic diameters of PCL‐g‐PNIPAAm micelles depend strongly on the graft length and density of the PNIPAAm segment, allowing to tune the particle size within a wide range. Additionally, the PCL‐g‐PNIPAAm micelles exhibit thermosensitive properties and aggregate when the temperature is above the lower critical solution temperature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41115.     

Thermoresponsive poly(ϵ‐caprolactone)‐graft‐poly(N‐isopropylacrylamide) graft copolymers prepared by a combination of ring‐opening polymerization and sequential azide–alkyne click chemistry

A straightforward strategy is described to synthesize poly(?‐caprolactone)‐graft‐poly(N‐isopropylacrylamide) (PCL‐g‐PNIPAAm) amphiphilic graft copolymers consisting of potentially biodegradable polyester backbones and thermoresponsive grafting chains. PCL with pendent chlorides was prepared by ring‐opening polymerization, followed by conversion of the pendent chlorides to azides. Alkyne‐terminated PNIPAAm was synthesized by atom transfer radial polymerization. Then, the alkyne end‐functionalized PNIPAAm was grafted onto the PCL backbone by a copper‐catalyzed azide–alkyne cycloaddition. PCL‐g‐PNIPAAm graft copolymers self‐assembled into spherical micelles comprised of PCL cores and PNIPAAm coronas. The critical micelle concentrations of the graft copolymers were in the range 7.8–18.2 mg L^?1, depending on copolymer composition. Mean hydrodynamic diameters of micelles were in the range 65–135 nm, which increased as the length of grafting chains grew. PCL‐g‐PNIPAAm micelles were thermosensitive and aggregated upon heating. © 2014 Society of Chemical Industry     

Synthesis of water‐soluble polyphenol‐graft‐poly(ethylene oxide) copolymers via enzymatic polymerization and anionic polymerization

Water‐soluble polyphenol‐graft‐poly(ethylene oxide) (PPH‐g‐PEO) copolymers were prepared using grafting‐through methodology. Polyphenol chains were synthesized via enzymatic polymerization of phenols, and the graft chains were synthesized via living anionic polymerization of ethylene oxides. The polymers were characterized using gel permeation chromatography, static light scattering and ¹H NMR, infrared and ultraviolet spectroscopies. The PPH‐g‐PEO graft copolymers are soluble in several common solvents, such as water, ethanol, N,N‐dimethylformamide, tetrahydrofuran and methylene dichloride. The solubility of the PPH‐g‐PEO graft copolymers is improved significantly compared with that of polyphenol. Copyright © 2009 Society of Chemical Industry     

Synthesis,characterization, and flocculation characteristics of polyacrylamide‐grafted glycogen

The synthesis of glycogen‐g‐polyacrylamide (Gly‐g‐PAM) was carried out by a ceric ion‐induced solution polymerization technique. Six grades of graft copolymers were synthesized by the variation of catalyst and monomer concentrations. These graft copolymers were characterized by intrinsic viscosity measurements, FTIR spectroscopy, and X‐ray diffraction techniques. Flocculation performance of these graft copolymers were done in kaolin suspension. Of the above grades, the graft copolymer Gly‐g‐PAM 5, which has longer PAM chains, showed best flocculation performance. The flocculation performance of the graft copolymer was compared with commercial flocculants and other PAM‐grafted flocculants developed so far in the authors' laboratory. In all the cases, it was found that the graft copolymer performed the best. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 773–778, 2007     

“Smart” membrane materials: Preparation and characterization of PVDF‐g‐PNIPAAm graft copolymer

In this research, a smart membrane material of graft copolymer of poly(vinylidene fluoride) with poly(N‐isopropylacrylamide) (PVDF‐g‐PNIPAAm) was synthesized by atom transfer radical polymerization (ATRP) using poly(vinylidene fluoride) (PVDF) as a macroinitiator and direct initiation of the secondary fluorinated site PVDF facilitates grafting the N‐isopropylacrylamide comonomer. The copolymers were characterized by Fourier transform infrared (FTIR), ¹H NMR, gel‐permeation chromatography (GPC), and X‐ray photoelectron spectroscopy (XPS). The temperature‐sensitive membrane was prepared from the PVDF‐g‐PNIPAAm graft copolymers by the phase inversion method. The effects of temperature on the flux of pure water of membrane was investigated. The results showed that alkyl fluorides were successfully applied as ATRP initiators in the synthetic condition and the flux of pure water through the PVDF‐g‐PNIPAAm membrane depended on the temperature change. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1482–1486, 2007     

CO2‐responsive polymer surfactant formed by noncovalent binding between dimethyl‐dodecylamine and alginate

A new kind of polymer surfactant, noncovalent binding between N,N‐dimethyl‐dodecylamine and alginate (C₁₂A‐Alg), was successfully prepared by mixing N,N‐dimethyl‐dodecylamine (C₁₂A) and sodium alginate (NaAlg) in the appropriate mole ratio and bubbling CO₂. C₁₂A was successfully grafted onto the alginate molecule by electrostatic interaction. The structure of C₁₂A‐Alg was confirmed by Fourier transform infrared and NMR spectroscopies. The polymer surfactant C₁₂A‐Alg has superior performance in foamability and emulsification. This foaming/defoaming and emulsification/demulsification behavior can be triggered by bubbling CO₂/N₂, demonstrating that the polymer surfactant C₁₂A‐Alg is switchable. © 2018 Society of Chemical Industry     

Poly(N‐isopropylacrylamide‐co‐hydroxyethyl methacrylate) graft copolymers and their application as carriers for drug delivery system

Poly(N‐isopropylacrylamide‐co‐hydroxyethyl methacrylate) [P(NIPAM‐co‐HEMA)] copolymer was synthesized by controlled radical polymerization from respective N‐isopropylacrylamide (NIPAM) and hydroxyethyl methacrylate (HEMA) monomers with a predetermined ratio. To prepare the thermosensitive and biodegradable nanoparticles, new thermosensitive graft copolymer, poly(L ‐lactide)‐graft‐poly(N‐isoporylacrylamide‐co‐hydroxyethyl methacrylate) [PLLA‐g‐P(NIPAM‐co‐HEMA)], with the lower critical solution temperature (LCST) near the normal body temperature, was synthesized by ring opening polymerization of L ‐lactide in the presence of P(NIPAM‐co‐HEMA). The amphiphilic property of the graft copolymers was formed by the grafting of the PLLA hydrophobic chains onto the PNIPAM based hydrophilic backbone. Therefore, the graft copolymers can self‐assemble into uniformly spherical micelles ò about 150–240 nm in diameter as observed by the field emission scanning electron microscope and dynamic light scattering. Dexamethasone can be loaded into these nanostructures during dialysis with a relative high loading capacity and its in vitro release depends on temperature. Above the LCST, most of the drugs were released from the drug‐loaded micelles, whereas a large amount of drugs still remains in the micelles after 48 h below the LCST. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Water‐soluble dual responsive polythiophene‐g‐poly(methoxyethoxy ethyl methacrylate)‐co‐poly(N,N‐diethylamino ethyl methacrylate) for different applications

Polythiophene (PT) based dual responsive water‐soluble graft copolymer (PT‐g‐[poly(methoxyethoxy ethyl methacrylate)‐co‐poly(N,N‐diethylamino ethyl methacrylate)]) (PT‐g‐P(MeO₂MA‐co‐DEAEMA)) (PTDE) has been synthesized by random copolymerization of methoxyethoxy ethyl methacrylate (MeO₂MA) and N,N‐diethylamino ethyl methacrylate (DEAEMA) at 30 °C on the 2,5‐poly(3‐[1‐ethyl‐2‐(2‐ bromoisobutyrate)] thiophene) (PTI) macroinitiator using the Cu based atom transfer radical polymerization technique. The PTDE graft copolymer was characterized by gel permeation chromatography and ¹H NMR techniques and it exhibits thermo‐reversible solubility in water showing a lower critical solution temperature of ca 42 °C in neutral aqueous solution. The PTDE graft copolymer contains a fluorescent PT backbone, and interestingly the system exhibits doubling of fluorescence intensity with rising temperature over the temperature range 41–45 °C at pH 7. The PTDE system therefore acts following the principle of the polymeric AND logic gate and it is also found to be effective in sensing of nitroaromatics, particularly picric acid. The influence of chain hydrophobicity on the logic operation and on the sensing of nitroaromatics is discussed. © 2014 Society of Chemical Industry     

Vesicular and micellar self‐assembly of stimuli‐responsive poly(N‐isopropyl acrylamide‐b‐9‐anthracene methyl methacrylate) amphiphilic diblock copolymers

Dually responsive amphiphilic diblock copolymers consisting of hydrophilic poly(N‐isopropyl acrylamide) [poly(NIPAAm)] and hydrophobic poly(9‐anthracene methyl methacrylate) were synthesized by reversible addition fragmentation chain‐transfer (RAFT) polymerization with 3‐(benzyl sulfanyl thiocarbonyl sulfanyl) propionic acid as a chain‐transfer agent. In the first step, the poly(NIPAAm) chain was grown to make a macro‐RAFT agent, and in the second step, the chain was extended by hydrophobic 9‐anthryl methyl methacrylate to yield amphiphilic poly(N‐isopropyl acrylamide‐b‐9‐anthracene methyl methacrylate) block copolymers. The formation of copolymers with three different hydrophobic block lengths and a fixed hydrophilic block was confirmed from their molecular weights. The self‐assembly of these copolymers was studied through the determination of the lower critical solution temperature and critical micelle concentration of the copolymers in aqueous solution. The self‐assembled block copolymers displayed vesicular morphology in the case of the small hydrophobic chain, but the morphology gradually turned into a micellar type when the hydrophobic chain length was increased. The variations in the length and chemical composition of the blocks allowed the tuning of the block copolymer responsiveness toward both the pH and temperature. The resulting self‐assembled structures underwent thermally induced and pH‐induced morphological transitions from vesicles to micelles and vice versa in aqueous solution. These dually responsive amphiphilic diblock copolymers have potential applications in the encapsulation of both hydrophobic and hydrophilic drug molecules, as evidenced from the dye encapsulation studies. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46474.     

Preparation and swelling properties of homopolymeric alginic acid fractions/poly(N‐isopropyl acrylamide) graft copolymers

Graft copolymers of crosslinked poly(N‐isopropyl acrylamide) (PNIPAAm) and homopolyguluronic acid (GG) and homopolymannuronic acid (MM) fractions of alginic acid were synthesized. MM and GG block fractions were obtained by partial acid hydrolysis of the alkaline extract from the brown seaweed Macrocystis pyrifera. The conjugation of these block fractions with the synthetic polymer was achieved by amidation with crosslinked PNIPAAm functionalized with an amino group at the end of the polymer chain. The structure of conjugates was determined by Fourier transform infrared and NMR spectroscopy. Atomic force microscopy of the graft copolymer GG‐g‐PNIPAAm showed a regular porous pattern, whereas the MM‐g‐PNIPAAm graft copolymer showed a regular netlike structure. Aqueous solutions of the synthesized graft copolymers afforded hydrogels by stirring with 0.1M CaCl₂. The hydrogels showed a well‐defined stimulus–response to temperature and pH. The swelling, thermal, and pH characterizations demonstrated the superior properties of the GG‐g‐PNIPAAm hydrogel over the MM‐g‐PNIPAAm hydrogel. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42398.     

Graft copolymerization of N‐vinyl‐2‐pyrrolidone onto sodium carboxymethylcellulose with azobisisobutyronitrile as the initiator

Graft copolymers of sodium carboxymethylcellulose with N‐vinyl‐2‐pyrrolidone were prepared in aqueous solutions with azobisisobutyronitrile as the initiator. The graft copolymers [sodium carboxymethylcellulose‐g‐poly(N‐vinyl‐2‐pyrrolidone)] were characterized with Fourier transform infrared spectroscopy, elemental analysis, nuclear magnetic resonance spectroscopy, differential scanning calorimetry, and scanning electron microscopy. The grafting parameters, including the graft yield of the graft copolymer and the grafting efficiency of the reaction, were evaluated comparatively. The effects of reaction variables such as the time, temperature, and monomer and initiator concentrations on these parameters were studied. The graft yield and grafting efficiency increased and then decreased with increasing concentrations of N‐vinyl‐2‐pyrrolidone and azobisisobutyronitrile and increasing polymerization temperatures. The optimum temperature and polymerization time were 70°C and 4.30 h, respectively. Further changes in the properties of grafted sodium carboxymethylcellulose, such as the intrinsic viscosity, were determined. The overall activation energy for the grafting was also calculated to be 10.5 kcal/mol. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 936–943, 2007     

Stimuli sensitive copolymer poly(N‐tert‐butylacrylamide‐ran‐acrylamide): Synthesis and characterization

Temperature sensitive random linear and crosslinked copolymers of N‐tert‐butylacrylamide (NTBA) and acrylamide (Am) were synthesized by the solution polymerization method, using regulated dosing of comonomer Am having a higher reactivity ratio (r_Am = 1.5) than NTBA (r_NTBA = 0.5). Copolymers with varying feed ratios of NTBA and Am (80 : 20 to 20 : 80 mol %) were synthesized and characterized. For the synthesis of copolymer hydrogels, N′, N‐methylene bisacrylamide (MBA) (1.13 mol %) was used along with monomers. The effect of composition on transition properties was evaluated for the linear copolymers and their hydrogels. A definite trend was observed. The incorporation of a higher percentage of the hydrophilic comonomer Am in the structure resulted in the shifting of the transition temperature towards a higher value. The transition temperatures of the copolymers synthesized with feed compositions of 80 : 20, 70 : 30, 60 : 40, 50 : 50, 40 : 60, 30 : 70, and 20 : 80 mol % were found to be 2, 10, 19, 27, 37, 45, and 58°C, respectively. Differential scanning calorimetry (DSC) studies confirmed the formation of random copolymers. The copolymers synthesized with a monomer feed ratio of 50 : 50 with regulated dosing showed a single glass transition temperature (T_g) at 168°C, while the copolymer synthesized with full dosing of Am at the beginning of the reaction showed two T_gs, at 134 and 189°C. The copolymer samples were analyzed by Fourier transform infrared spectroscopy (FTIR) for ascertaining the composition. The composition of the copolymers followed the trend of the feed ratio, but the incorporation of NTBA in the copolymers was found to be lower than the feed ratio because of lower than quantitative yields of the reactions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 672–680, 2005