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     

Preparation of poly(divinylbenzene‐co‐N‐isopropylacrylamide) microspheres and their hydrogen‐bonding assembly behavior for raspberry‐like core‐corona polymer composite

Narrowdisperse poly(divinylbenzene‐co‐N‐isopropylacrylamide) (poly(DVB‐co‐NIPAM)) functional microspheres with the diameter in the range of 630 nm and 2.58 μm were prepared by distillation–precipitation polymerization in neat acetonitrile in the absence of any stabilizer. The effect of N‐isopropylacrylamide (NIPAM) ratio in the comonomer feed on the morphology of the resultant polymer particles was investigated in detail with divinylbenzene (DVB) as crosslinker and 2,2′‐azobisisobutyronitrile (AIBN) as initiator. The monodisperse poly(DVB‐co‐NIPAM) microspheres with NIPAM fraction of 20 wt % were selected for the preparation of raspberry‐like core‐corona polymer composite by the hydrogen‐bonding self‐assembly heterocoagulation with poly(ethyleneglycol dimethacrylate‐co‐acrylic acid) [poly(EGDMA‐co‐AA)] nanospheres. Both of the functional poly(DVB‐co‐NIPAM) microspheres and the core‐corona particles were characterized with scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), and elemental analysis (EA). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1350–1357, 2007     

Release behavior of freeze‐dried alginate beads containing poly(N‐isopropylacrylamide) copolymers

Beads composed of alginate, poly(N‐isopropylacrylamide) (PNIPAM), the copolymers of N‐isopropylacrylamide and methacrylic acid (P(NIPAM‐co‐MAA)), and the copolymers of N‐isopropylacrylamide, methacrylic acid, and octadecyl acrylate (P(NIPAM‐co‐MAA‐co‐ODA)), were prepared by dropping the polymer solutions into CaCl₂ solution. The beads were freeze‐dried and the release of blue dextran entrapped in the beads was observed in distilled water with time and pH. The degree of release was in the order of alginate bead < alginate/PNIPAM bead ≈ alginate/P(NIPAM‐co‐MAA) bead < alginate/P(NIPAM‐co‐MAA‐co‐ODA) bead. On the other hand, swelling ratios reached steady state within 20 min, and the values were 200–800 depending on the bead composition. The degree of swelling showed the same order as that of release. Among the beads, only alginate/P(NIPAM‐co‐MAA‐co‐ODA) bead exhibited pH‐dependent release. At acidic condition, inter‐ and intraelectrostatic repulsion is weak and P(NIPAM‐co‐MAA‐co‐ODA) could readily be assembled into an aggregate due to the prevailing hydrophobic interaction of ODA. Thus, it could block the pore of bead matrix, leading to a suppressed release. © 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     

Poly(N‐isopropylacrylamide‐co‐sodium acrylate) hydrogels: Interactions with surfactants

Poly(N‐isopropylacrylamide‐co‐sodium acrylate) [poly(NIPAM‐co‐SA)] hydrogels were modified with three different kind of surfactants (cationic, anionic, and nonionic) to study the effect on the swelling properties. The structural variation of the surfactant‐modified hydrogels was investigated in detail. The interaction between the surfactants and the hydrogel varies and strictly depends on the surfactant type. The variation in thermal stability of the modified surfactant hydrogels was investigated and compared with unmodified hydrogel. Further, the hydrogel swelling/diffusion kinetic parameters were investigated and diffusion of water into hydrogel was found to be of the non‐Fickian transport mechanism. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3423–3430, 2007     

Poly(N‐isopropylacrylamide) grafted to a strongly charged backbone: Thermoresponsive behavior in aqueous solution

The thermoresponsive properties in aqueous solution of the graft copolymer poly(acrylic acid‐co‐2‐acrylamido‐2‐methyl propane sulfonic acid)‐g‐poly(N‐isopropylacrylamide) [P(AA‐co‐AMPSA)‐g‐PNIPAM] were studied and compared to the corresponding behavior of the poly(acrylic acid)‐g‐poly(N‐isopropylacrylamide) (PAA‐g‐PNIPAM) graft product. Both products contain about 40% (w/w) of PNIPAM, whereas the backbone, P(AA‐co‐AMPSA), of the first copolymer contains about 40% of AMPSA mole units. The strongly charged P(AA‐co‐AMPSA)‐g‐PNIPAM graft copolymer was water soluble over the whole pH range, whereas the PAA‐g‐PNIPAM copolymer precipitated out from water at pH < 4. As a result, the first product exhibited a temperature‐sensitive behavior in a wide pH range, extended in the acidic region, whereas in semidilute aqueous solutions, an important thermothickening behavior was observed, even at low pH (pH = 3.0). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3466–3470, 2004     

Microwave‐assisted preparation of temperature sensitive poly(N‐isopropylacrylamide) hydrogels in poly(ethylene oxide)‐600

In this article, a series of poly(N‐isopropylacrylamide) (PNIPAM)‐based hydrogels were prepared under microwave irradiation using poly(ethylene oxide)‐600 (PEO‐600) as reaction medium and microwave‐absorbing agent as well as pore‐forming agent. All of the temperature measurements, gel fractions, and FTIR analyses proved that the PNIPAM hydrogels were successfully synthesized. Within 1 min, the PNIPAM hydrogel with a 98% yield was obtained under microwave irradiation. The PNIPAM hydrogels thus prepared exhibited controllable properties such as pore size, equilibrium swelling ratios, and swelling/deswelling rates when changing the feed weight ratios of monomer (N‐isopropylacrylamide, NIPAM) to PEO‐600. These properties are well adapted to the different requirements for their potential application in many fields such as biomedicine. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:4177–4184, 2006     

Rheological properties of thermoresponsive nanocomposite hydrogels

Highly elastic and robust nanocomposite hydrogels based on N‐isopropylacrylamide (NIPAM) and cationic (3‐acrylamidopropyl) trimethylammonium chloride (AMPTMA) were synthesized by photopolymerization. Nanoscopic clay, laponite XLS, was added in the gels during the synthesis. The effect of a hydrophobic salt, lithium bis(trifluoromethane) sulfonimide (LiNTf₂), and clay content on the viscoelastic properties, swelling ratio, and stiffness of the nanocomposite hydrogels were investigated as a function of temperature. Synthetic clay served as a multifunctional cross‐linker, producing hydrogels with enhanced elastic properties. Anionic NTf₂ binds to the cationic comonomer units and significantly affected the viscoelasticity and thermal properties. DSC measurements showed that the volume phase transition temperature and its enthalpy changed with the clay content and with introducing the cationic comonomer (AMPTMA) in the PNIPAM network. With the addition of either laponite XLS or the comonomer and 5 mM solution of LiNTf₂, a fourfold and fivefold increase in elastic modulus was obtained, respectively, compared to that of the homopolymer PNIPAM hydrogel. With increasing the temperature from 20 to 45°C for the copolymer gel with 10% AMPTMA in 5 mM LiNTf₂, the elastic modulus grew 15 times larger. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43123.     

Poly(N‐isopropylacrylamide) hydrogel: Effect of hydrophilicity on controlled release of ibuprofen at different pH

Stimuli‐sensitive drug delivery systems (DDSs) have attracted considerable attention in medical and pharmaceutical fields; thermo‐sensitive DDS dealing with poly(N‐isopropylacrylamide) (PNIPAM) have been widely studied. Hydrogels composed of temperature‐sensitive NIPAM and biocompatible and pH‐sensitive maleic acid (MAc) were synthesized by sedimentation polymerization. Experiments on drug release from the crosslinked NIPAM‐co‐MAc hydrogel loaded with ibuprofen into different pH buffer solutions were successfully carried out at temperature swing between 25 and 40°C. The in vitro release studies have showed that the release rate depended on acidity or basicity (polarity) of the medium and the gel and swelling ratio of the gel network as a function of the environmental pH and temperature. The SEM image of the dry bead gave more insight into the surface architecture and the thermal studies shine light on the decomposition pattern and glass transition temperature of the gel. The mechanism of the drug release was discussed in relation to the diffusion rate and the abrupt change in the pH of the medium. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of poly(sodium acrylate‐co‐sodium 1‐(acryloyloxy) propan‐2‐yl phosphate) and comparative study on its swelling properties with poly(sodium acrylate) and poly(sodium acrylate‐co‐2‐hydroxypropyl acrylate)

A new superabsorbent copolymer, poly(sodium acrylate‐co‐sodium 1‐(acryloyloxy) propan‐2‐yl phosphate) [P(SA‐co‐SAPP)], was synthesized by a novel prepared monomer, 1‐(acryloyloxy) propan‐2‐yl phosphoryl dichloride. The swelling properties of the superabsorbent were investigated by comparison with poly(sodium acrylate) (PSA) and the copolymer of poly(sodium acrylate‐co‐2‐hydroxypropyl acrylate) [P(SA‐co‐HPA)]. The results showed that (1) the superabsorbent containing sodium 1‐(acryloyloxy) propan‐2‐yl phosphate had higher water absorbency at general testing conditions; (2) the swelling properties of P(SA‐co‐SAPP) and PSA were obviously influenced by pH of solutions, which were different from that of P(SA‐co‐HPA); (3) the swelling process and the saturated water absorbency of all superabsorbents were remarkably affected by cations, especially multivalent ones, while barely affected by anions. POLYM. ENG. SCI., 47:728–737, 2007. © 2007 Society of Plastics Engineers.     

Synthesis and characterization of novel,temperature‐sensitive microgels based on N‐isopropylacrylamide and tert‐butyl acrylate

A series of temperature‐sensitive microgels based on N‐isopropylacrylamide as the main monomer, tert‐butyl acrylate (tBA) as the comonomer, and N,N′‐methylene‐bis(acrylamide) as the crosslinker were synthesized with a modified surfactant‐free emulsion polymerization method. The chemical structure and global shape with an excellent monodispersity of the microgels were confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The temperature‐sensitive behavior of the microgels was investigated by dynamic light scattering and ultraviolet–visible spectrophotometric analysis. The results show that the volume phase‐transition temperature of the poly(N‐isopropylacrylamide‐co‐tert‐butyl acrylate) [poly(NIPAM‐co‐tBA)] microgels were tuned over a broad range by the incorporated amount of tBA comonomer and their temperature sensitivity decreased with increasing content of tBA units incorporated into the microgel network. Furthermore, the swelling ratios of the poly (NIPAM‐co‐tBA) microgels were lowered gradually with increasing tBA unit content within the microgel network. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2962–2967, 2007     

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     

Preparation of toughened polypropylene‐g‐poly(butyl acrylate‐co‐acrylated castor oil) by suspension grafting polymerization

Butyl acrylate (BA) with acrylated castor oil (ACO) was grafted onto porous polypropylene (PP) granules by grafting polymerization. Crosslinked copolymer microdomains which functioned as rubber phase to improve the toughness of PP were filled into the pores of PP granules. The sizes of crosslinked copolymer microdomains were controlled in the range of 0.1–1 μm in PP matrix. The results of fourier transform infrared spectroscopy and scanning electron microscope of PP‐g‐(BA‐co‐ACO) after extracted by acetone confirmed that BA and ACO were grafted onto PP successfully. The effects of comonomer ratio, initiator content and comonomer content on grafting percentage (GP) and grafting efficiency (GE) were investigated. The GP of PP‐g‐(BA‐co‐ACO) could be up to 21.3% with the comonomer content increasing to 25%. The crosslinked copolymer decreased the melting flow index and the relative crystallinity of PP. Dynamic mechanical thermal analysis showed that the glass transition temperature of PP decreased slightly from 22°C to 15°C. The addition of 5% comonomer content led to an increase of notched impact strength from 1.96 to 3.81 kJ/m² (nearly doubled) and a marginal decrease in the tensile strength of PP. Then with further addition of comonomer, the notched impact strength increased to 8.98 kJ/m² while the tensile strength was 29.37 MPa. POLYM. ENG. SCI., 58:86–93, 2018. © 2017 Society of Plastics Engineers     

Preparation and characterization of poly(ϵ‐caprolactone‐co‐p‐dioxanone)–poly(ethylene glycol)–poly(ϵ‐caprolactone‐co‐p‐dioxanone)/bioactive inorganic particle nanocomposites

With an aim to develop injectable hydrogel with improved solution stability and enhanced bone repair function, thermogelling poly(ε‐caprolactone‐co‐p‐dioxanone)‐poly(ethylene glycol)‐poly(ε‐caprolactone–co‐p‐dioxanone) (PECP)/bioactive inorganic particle nanocomposites were successfully prepared by blending the triblock copolymer (PECP) with nano‐hydroxyapatite (n‐HA) or nano‐calcium carbonate (n‐CaCO₃). The hydrogel nanocomposites underwent clear sol–gel transitions with increasing temperature from 0 to 50°C. The obtained hydrogel nanocomposites were investigated by ¹H NMR, FT‐IR, TEM, and DSC. It was found that the incorporation of inorganic nanoparticles into PECP matrix would lead to the critical gelation temperature (CGT) shifting to lower values compared with the pure PECP hydrogel. The CGT of the hydrogel nanocomposites could be effectively controlled by adjusting PECP concentration or the content of inorganic nanoparticles. The SEM results showed that the interconnected porous structures of hydrogel nanocomposites were potentially useful as injectable scaffolds. In addition, due to the relatively low crystallinity of PECP triblock copolymer, the aqueous solutions of the nanocomposites could be stored at low temperature (5°C) without crystallization for several days, which would facilitate the practical applications. The PECP/bioactive inorganic particle hydrogel nanocomposites are expected to be promising injectable tissue engineering materials for bone repair applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A novel temperature and pH dual‐responsive hybrid hydrogel with polyhedral oligomeric silsesquioxane as crosslinker: synthesis,characterization and drug release properties

Octavinyl polyhedral oligomeric silsesquioxane (OVPS) is used as the crosslinker instead of N,N′‐methylenebisacrylamide (BIS) to copolymerize with 2‐(dimethylamino)ethyl methacrylate (DMAEMA) or DMAEMA and N‐isopropylacrylamide (NIPAM) to prepare hybrid hydrogels: P(OVPS‐co‐DMAEMA) and P(OVPS‐co‐DMAEMA‐co‐NIPAM). The prepared hydrogels are transparent and show dual response to temperature and pH. The hydrogels were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis and tensile tests. Their mechanical properties, swelling ratio, deswelling and reswelling behaviors as well as drug release properties were investigated. The results indicate that OVPS can be incorporated into polymer networks in proportion to feed ratios. The P(OVPS‐co‐DMAEMA) hydrogel exhibits more homogeneous interior structure, higher swelling ratio and faster response than the conventional hydrogel prepared with BIS. Moreover, the incorporation of OVPS enhances the compression and tensile properties of the hydrogels. The feed ratios of OVPS and NIPAM have a great effect on volume phase transition temperature, thermal sensitivity, swelling behavior, mechanical properties and drug release properties of the hybrid hydrogels. The prepared dual‐responsive OVPS‐containing hydrogels are expected to be used as biomedical materials in drug release and tissue engineering. © 2014 Society of Chemical Industry     

Preparation and characterization of poly(N‐tert‐butylacrylamide‐co‐acrylamide) ferrogel

Magnetic‐field‐sensitive gel, called ferrogel, was prepared by a two‐step procedure in which first step requires synthesis of the poly(N‐tert‐butylacrylamide‐co‐acrylamide) [P(NTBA‐co‐AAm)] hydrogel and during second step magnetite (Fe₃O₄) particles were formed in the hydrogel via coprecipitation of Fe(II) and Fe(III) ions in alkaline medium at 70°C. The obtained ferrogel was characterized by attenuated total reflectance Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy combined with energy dispersive spectroscopy, and electron spin resonance measurements. The magnetic responsive of the ferrogel was also investigated by applying magnetic field to the ferrogel. The extent of a bending degree of the ferrogel depends on the applied magnetic field strength. In addition, the magnetic responsive studies also indicated that formed magnetite content in the hydrogel is high enough to achieve considerable magnetic response to external magnetic field. As a result, the P(NTBA‐co‐AAm) ferrogel may be useful for potential applications in magnetically controlled drug release systems, magnetic‐sensitive sensors, and pseudomuscular actuators. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Studies on comonomer compositional distribution and its effect on some physical properties of bacterial poly(3‐hydroxybutyric acid‐co‐3‐hydroxypropionic acid)

Comonomer compositional distribution of bacterially synthesized poly(3‐hydroxybutyric acid‐co‐3‐hydroxypropionic acid) [P(3HB‐co‐3HP)] was investigated via solvent/non‐solvent fractionation techniques. The result indicates the presence of extremely broad comonomer compositional distribution in the original bacterial product. Furthermore, utilizing compositionally fractionated bacterial copolyesters with much narrower comonomer compositional distributions, the 3HP comonomer content‐dependence of their thermal and crystallization behavior was studied by means of differential scanning calorimeter (DSC) and polarized optical microscopy and the results compared with those of unfractionated copolyesters. It was revealed that the physical features of the fractionated copolyester P(3HB‐co‐3HP)s strongly depends on the 3HP comonomer content. In addition, to clarify the effect of the compositional distribution on the properties of the unfractionated copolyester, the miscibility between bacterial poly(3‐hydroxybutyric acid) [P(3HB)] and two fractionated P(3HB‐co‐3HP) samples with 11.3 and 14.9% 3HP was investigated for blends obtained by solvent casting techniques. The evidence of thermal analysis and spherulitic growth rates imply miscibility of the P(3HB)/3HB‐rich P(3HB‐co‐3HP) binary blends. © 1999 Society of Chemical Industry     

Siloxane‐based copolymers for use in two‐phase partitioning bioreactors

Two‐phase partitioning bioreactors (TPPBs) have been recently demonstrated to be capable of using solid polymers as the absorbing/desorbing phase. In this paper, we examine the possibility of using a siloxane‐based copolymer as this phase. Copolymers were prepared using vinyl terminated oligo(dimethylsiloxane‐co‐diphenylsiloxane), copolymerized with varying amounts of the comonomers ethylene glycol dimethacrylate (EGDMA), N‐vinyl pyrrolidone (NVP), or acrylic acid (AA), via free radical polymerization. The absorption rate of phenol as a representative pollutant into these polymers from water was measured. The inclusion of a water‐soluble comonomer resulted in swelling of the polymers in water, enhanced total phenol absorption, but reduced phenol diffusivity.     

The structure characterization of thermosensitive poly(N‐isopropylacrylamide‐co‐2‐hydroxypropyl methacrylate) hydrogel

The goal of this work was to investigate a possible way of crosslinking polymer chains and the potential formation of intramolecular hydrogen bonds in thermosensitive poly(N‐isopropylacrylamide‐co‐2‐hydroxypropyl methacrylate) (p(NIPAM‐HPMet)) hydrogels obtained by radical polymerization. The chemical structure of the synthesized hydrogels was investigated by Fourier transform infrared (FTIR) spectroscopy and XRD. The FTIR spectrum confirmed the presence of hydrogen bonds formed between the chains in the copolymer. XRD analysis confirmed the amorphous ? crystalline structure of the copolymer. A three‐glass transition and two melting temperatures were detected by DSC. It was found that the addition of HPMet increased the glass transition and melting temperatures of the p(NIPAM‐HPMet) copolymer. The swelling transport mechanism of p(NIPAM‐HPMet) changed from non‐Fickian at 20 °C to case III or zero‐order time‐independent kinetics characterized by a linear mass uptake with time with increasing temperature at 40 °C. © 2013 Society of Chemical Industry     

Polymer–metal composite particles: Metal particles on poly(St‐co‐MAA) microspheres

Poly(styrene‐co‐methacrylic acid) P(St‐co‐MAA) microspheres with a monodisperse size distribution were prepared by emulsifier‐free emulsion copolymerization of St and MAA. The effects of MAA content on the polymerization rate and the content of MAA in the copolymer were investigated by gravimetrical and IR methods, respectively. The results of XPS measurement indicated the presence of a carboxyl functional group. By chemical metal deposition, nickel or palladium particles were formed and deposited on the surface of P(St‐co‐MAA) microspheres to form P(St‐co‐MAA)Ni or P(St‐co‐MAA)Pd composite particles. XRD measurement and TEM observation confirmed that nickel and palladium metal particles in a small size (20–40 nm) were distributed on surface of the copolymer microspheres. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1693–1698, 2000