Synthesis and properties of polycarbonate copolymers of trimethylene carbonate and 2‐phenyl‐5,5‐bis(hydroxymethyl) trimethylene carbonate

The polycarbonate copolymers poly[trimethylene carbonate‐co‐2‐phenyl‐5,5‐bis(hydroxymethyl) trimethylene carbonate] [P(TMC‐co‐PTC)] were synthesized by the ring‐opening polymerization of trimethylene carbonate (TMC) and 2‐phenyl‐5,5‐bis(hydroxymethyl) trimethylene carbonate (PTC) with tin(II) 2‐ethylhexanoate and aluminum isopropoxide as the catalysts. These copolymers were further reduced by a palladium/carbonate (Pd/C; 10%) catalyst to produce partly deprotected copolymers. These two types of copolymers were characterized by ¹H‐NMR, Fourier transform infrared spectroscopy, UV spectroscopy, gel permeation chromatography, differential scanning calorimetry, and an automatic contact angle meter. The influences of the feed molar ratio of the monomers, the catalyst concentration, the reaction time, and the reaction temperature on the copolymerization process were also studied. The copolymerization of the TMC and PTC monomers was a nonideal copolymerization, and the copolymerization reactivity ratio of TMC was higher than that of PTC. In vitro degradation tests indicated that the partly deprotected copolymers possessed faster degradation rates and more hydrophilicity than the corresponding unreduced copolymers. Moreover, the degradation of these two type copolymers increased when the pH value of the buffer solutions decreased. In vitro drug‐release experiments showed that these two types of copolymers had steady drug‐release rates and good controlled release properties. Moreover, the partly deprotected copolymers had faster drug‐release rates than the corresponding unreduced copolymers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and drug‐release behavior of minocycline‐loaded poly[hydroxyethyl methacrylate‐co‐poly(ethylene glycol)–methacrylate] films

In this work, biocompatible hydrogel matrices for wound‐dressing materials and controlled drug‐release systems were prepared from poly[hydroxyethyl methacrylate‐co‐poly(ethylene glycol)–methacrylate] [p(HEMA‐co‐PEG–MA] films via UV‐initiated photopolymerization. The characterization of the hydrogels was conducted with swelling experiments, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis (differential scanning calorimetry), and contact‐angle studies. The water absorbency of the hydrogel films significantly changed with the change of the medium pH from 4.0 to 7.4. The thermal stability of the copolymer was lowered by an increase in the ratio of poly(ethylene glycol) (PEG) to methacrylate (MA) in the film structure. Contact‐angle measurements on the surface of the p(HEMA‐co‐PEG–MA) films demonstrated that the copolymer gave rise to a significant hydrophilic surface in comparison with the homopolymer of 2‐hydroxyethyl methacrylate (HEMA). The blood protein adsorption was significantly reduced on the surface of the copolymer hydrogels in comparison with the control homopolymer of HEMA. Model antibiotic (i.e., minocycline) release experiments were performed in physiological buffer saline solutions with a continuous flow release system. The amount of minocycline release was shown to be dependent on the HEMA/PEG–MA ratio. The hydrogels have good antifouling properties and therefore are suitable candidates for wound dressing and other tissue engineering applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of double‐hydrophilic poly(methylacrylic acid)–poly(ethylene glycol)–poly(methylacrylic acid) triblock copolymers and their micelle formation

The aim of the work reported was to synthesize a series of double‐hydrophilic poly(methacrylic acid)‐block‐poly(ethylene glycol)‐block‐poly(methacrylic acid) (PMAA‐b‐PEG‐b‐PMAA) triblock copolymers and to study their self‐assembly behavior. These copolymeric self‐assembly systems are expected to be potential candidates for applications as carriers of hydrophilic drugs. Bromo‐terminated difunctional PEG macroinitiators were used to synthesize well‐defined triblock copolymers of poly(tert‐butyl methacrylate)‐block‐poly(ethylene glycol)‐block‐poly(tert‐butyl methacrylate) via reversible‐deactivation radical polymerization. After the removal of the tert‐butyl group by hydrolysis, double‐hydrophilic PMAA‐b‐PEG‐b‐PMAA triblock copolymers were obtained. pH‐sensitive spherical micelles with a core–corona structure were fabricated by self‐assembly of the double‐hydrophilic PMAA‐b‐PEG‐b‐PMAA triblock copolymers at lower solution pH. Transmission electron microscopy and laser light scattering studies showed the micelles were of nanometric scale with narrow size distribution. Solution pH and micelle concentration strongly influenced the hydrodynamic radius of the spherical micelles (48–310 nm). A possible reason for the formation of the micelles is proposed. Copyright © 2010 Society of Chemical Industry     

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     

Effect of drug loading on the properties of temperature‐responsive polyester–poly(ethylene glycol)–polyester hydrogels

Hydrogels that can undergo gelation upon injection in vivo are promising systems for the site‐specific delivery of drugs. In particular, some thermo‐responsive gels require no chemical additives but simply gel in response to a change from a lower temperature to physiological temperature (37 °C). The gelation mechanism does not involve covalent bonds, and it is possible that incorporation of drugs into the hydrogel could disrupt gelation. We investigated the incorporation of drugs into thermo‐responsive hydrogels based on poly(?‐caprolactone‐co‐lactide)‐block‐poly(ethylene glycol)‐block‐poly(?‐caprolactone‐co‐lactide) (PCLA–PEG–PCLA). Significant differences in properties and in the response to incorporation of the anti‐inflammatory drug celecoxib (CXB) were observed as the PEG block length was varied from 1500 to 3000 g mol^?1. Linear viscoelastic moduli of a PCLA–PEG–PCLA hydrogel containing a 2000 g mol^?1 PEG block were least affected by the incorporation of CXB and this gel also exhibited the slowest release of CXB, so the incorporation of phenylbutazone, methotrexate, ibuprofen, diclofenac and etodolac was also investigated for this hydrogel. Different drugs resulted in varying degrees of syneresis of the hydrogels, suggesting that they interact with the polymer networks in different ways. In addition, the drugs had varying effects on the viscoelastic and compressive moduli of the gels. The results showed that the effects of drug loading on the properties of thermo‐responsive hydrogels can be substantial and depend on the drug. For applications such as intra‐articular drug delivery, in which the mechanical properties of the hydrogel are important, these effects should thus be studied on a case‐by‐case basis. © 2019 Society of Chemical Industry     

Tough and Enzyme‐Degradable Hydrogels

Mechanically robust hydrogels that degrade only via cell action have potential as scaffolds for the generation of load‐bearing soft connective tissue. This study demonstrates that terminally acrylated 4‐arm‐poly(ethylene glycol)‐block‐oligo(trimethylene carbonate) (4a‐PEG‐(TMC)_n) can be readily reacted with a collagenase‐degradable bis‐cysteine peptide to form hydrogels. The inclusion of the TMC blocks renders the hydrogels mechanically tough when tested under compression, with modulus and toughness values within the range of those of articular cartilage. Moreover, the hydrogels formed are resistant to degradation by hydrolysis in the absence of collagenase but degrade via surface erosion in the presence of collagenase. The strategy employed to form these hydrogels is readily tailored to create a variety of tough, enzyme‐degradable hydrogels of varying mechanical and degradation properties.     

Toughened poly(trimethylene terephthalate) by blending with a functionalized ethylene–propylene–diene copolymer

A series of blends of poly(trimethylene terephthalate) (PTT) with ethylene–propylene–diene copolymer grafted with maleic anhydride (EPDM‐g‐MA) were prepared in composition by weight 95/5, 90/10, 80/20, and 70/30. Their morphologies, crystallization behavior, and mechanical properties were investigated. Morphology observation shows the well‐dispersed domains of EPDM‐g‐MA in PTT matrix with weight‐average particle size from 0.98 to 3.64 μm when the EPDM‐g‐MA content increases from 5% to 30% (mass fraction) in the blends. The constancy of the crystallinity level indicates that the elastomeric phase does not disturb the crystallization process of PTT. The addition of rubbery EPDM‐g‐MA to PTT matrix increases the notched Izod impact strength, but impairs the tensile strength properties. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Synthesis and surface‐active properties of a trisiloxane‐modified oligo(propylene oxide‐block‐ethylene oxide) wetting agent

Polydisperse 1,1,1,3,5,5,5‐heptamethyltrisiloxane‐oligo(propylene oxide‐block‐ethylene oxide) wetting agents were synthesized through the hydrosilylation of 1,1,1,3,5,5,5‐heptamethyltrisiloxane (HMTS) with active hydrogen and allyl oligo(propylene oxide‐block‐ethylene oxide) [allyl oligo(PO‐b‐EO)] with hexachloro dihydrogen platinate(IV) as a catalyst. Allyl oligo(PO‐b‐EO) with a hydrophilic–hydrophobic balance was synthesized through the combination of propylene oxide (PO) and ethylene oxide with allyl alcohol. The wetting agents with a hydrophilic–hydrophobic balance were synthesized. The aqueous solutions of the wetting agents (0.1 wt %) were almost visibly turbid. An increase in the number of hydrophobic groups of HMTS and PO for the wetting agents resulted in a lower critical solution temperature. Lower surface tensions of 20–25 dyn/cm were found above the critical micelle concentration (cmc), and they decreased with an increase in the number of hydrophobic groups. The cmc's were below 0.01 wt %, decreasing with as the number of hydrophobic groups increased. The wetting power and emulsion stability for the oil‐in‐water systems increased as the concentration of the wetting agents increased, and they decreased as the number of hydrophobic groups increased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3292–3302, 2004     

Thermoresponsive poly(γ‐propyl‐l‐glutamate)‐graft‐(oligo ethylene glycol)s: Synthesis,characterization, and properties

A series of thermoresponsive poly(γ‐propyl‐_L‐glutamate)‐graft‐(oligo ethylene glycol)s (PPLG‐g‐OEGs) with different main‐chain and side‐chain lengths have been synthesized via copper‐mediated alkyne‐azide 1,3‐dipolar cycloaddition between poly(γ‐azidopropyl‐_L‐glutamate)s (PAPLG) and propargyl terminated oligo ethylene glycols (Pr‐OEGs). Fourier transform infrared spectrometer analysis revealed that PAPLG₁₀ adopted 39.4% β‐sheet, 47.4% α‐helix, and 13.2% random coil while PAPLG with longer main‐chain length (DP = 37 and 88) and PPLG‐g‐OEGs adopted exclusive α‐helix in the solid state. Circular dichroism analysis revealed that PPLG‐g‐OEGs adopted α‐helical conformations with helicities in the range of 50～100%. The thermoresponsive behaviors of PPLG‐g‐OEGs in water have been studied by dynamic light scattering. The polymer concentration, main‐/side‐chain length, and helicity collectively affected their cloud point temperatures. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41022.     

Temperature‐responsive properties of poly(acrylic acid‐co‐acrylamide)‐graft‐oligo(ethylene glycol) hydrogels

A series of temperature‐ and pH‐responsive hydrogels were prepared from acrylic acid (AAc), acrylamide (AAm), oligo(ethylene glycol)monoacrylate (OEGMA), and oligo(ethylene glycol)diacrylate by varying the AAc:AAm molar ratio and the OEGMA content. Phase‐transition temperatures and swelling ratios of the obtained poly(AAc‐co‐AAm)‐graft‐OEG gels were measured as a function of temperature and pH. At pH < 5, the obvious transition temperatures ranging from 5 to 35°C were obtained as the AAc : AAm molar ratio was varied. The highest transition temperature was obtained at the AAc : AAm ratios of 5 : 5 and 6 : 4, and the sharp transition curves were observed at the AAc : AAm ratios from 5 : 5 to 8 : 2. The transition temperature further increased with increasing OEGMA content. It was suggested that OEG graft chains with a large mobility played an important role for the formation of hydrogen bonding in the hydrogels. The gels prepared here showed obvious reproducibility of the phase transition in response to temperature changes, which suggests the feasibility of their practical applications. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 798–805, 2001     

Property enhancement in polypropylene ternary blend nanocomposites via a novel poly(ethylene oxide)‐grafted polystyrene‐block‐poly(ethylene/butylene)‐block‐polystyrene toughener–compatibilizer system

Synthesis and characterization of a novel toughener–compatibilizer for polypropylene (PP)–montmorillonite (MMT) nanocomposites were conducted to provide enhanced mechanical and thermal properties. Poly(ethylene oxide) (PEO) blocks were synthetically grafted onto maleic anhydride‐grafted polystyrene‐block‐poly(ethylene/butylene)‐block‐polystyrene (SEBS‐g‐MA). Special attention was paid to emphasize the effect of PEO‐grafted SEBS (SEBS‐g‐PEO) against SEBS‐g‐MA on morphology, static/dynamic mechanical properties and surface hydrophilicity of the resultant blends and nanocomposites. It was found that the silicate layers of neat MMT are well separated by PEO chains chemically bonded to nonpolar SEBS polymer without needing any organophilic modification of the clay as confirmed by X‐ray diffraction and transmission electron microscopy analyses. From scanning electron microscopy analyses, elastomeric domains interacting with MMT layers via PEO sites were found to be distributed in the PP matrix with higher number and smaller sizes than the corresponding blend. As a benefit of PEO grafting, SEBS‐g‐PEO‐containing nanocomposite exhibited not only higher toughness/impact strength but also increased creep recovery, as compared to corresponding SEBS‐g‐MA‐containing nanocomposite and neat PP. The damping parameter of the same nanocomposite was also found to be high in a broad range of temperatures as another advantage of the SEBS‐g‐PEO toughener–compatibilizer. The water contact angles of the blends and nanocomposites were found to be lower than that of neat hydrophobic PP which is desirable for finishing processes such as dyeing and coating. © 2018 Society of Chemical Industry     

Synthesis and characterization of poly(methylphenylsilylene)–poly(ethylene oxide) and poly(methylphenylsilylene)–polyisoprene multiblock copolymers

Multiblock copolymers were synthesized through condensation reactions of end‐groups of α,ω‐dichloro‐poly(methylphenylsilylene) with hydroxyl end‐groups of poly(ethylene glycol) or the chain‐ends of ‘living’ polyisoprenyl disodium. Optimum conditions have been sought through kinetic studies and by investigation of model reactions. The overall molecular weight distribution of poly(methylphenylsilylene)‐block‐poly(ethylene oxide) is characterized in terms of Flory's theory of condensation reactions, while the limiting step in the reaction is tentatively attributed to the formation of aggregates. © 2001 Society of Chemical Industry     

Non‐catalyst synthesis and in vitro drug release property of poly(5,5‐dimethyl‐1,3‐dioxan‐2‐one)‐block‐methoxy poly(ethylene glycol) copolymers

A series of poly(5,5‐dimethyl‐1,3‐dioxan‐2‐one)‐block‐methoxy poly(ethylene glycol) (PDTC‐b‐mPEG) copolymers were synthesized by the ring‐opening polymerization of 5,5‐dimethyl‐1,3‐dioxan‐2‐one (DTC) in bulk, using methoxy poly(ethylene glycol) (mPEG) as initiator without adding any catalysts. The resulting copolymers were characterized by Fourier transform infrared spectra, ¹H NMR and gel permeation chromatography. The influences of some factors such as the DTC/mPEG molar feed ratio, reaction time and reaction temperature on the copolymerization were investigated. The experimental results showed that mPEG could effectively initiate the ring‐opening polymerization of DTC in the absence of catalyst, and that the copolymerization conditions had a significant effect on the molecular weight of PDTC‐b‐mPEG copolymer. In vitro drug release study demonstrated that the amount of indomethacin released from PDTC‐b‐mPEG copolymer decreased with increase in the DTC content in the copolymer. © 2013 Society of Chemical Industry     

Polycarbonate microspheres containing tumor necrosis factor‐α genes and magnetic powder as potential cancer therapeutics

Amphiphilic polycarbonate copolymers including methoxy‐terminated poly(ethylene glycol)‐co‐poly (5,5‐dimethyl trimethylene carbonate) [Poly(PEG‐b‐TMC)] and poly(ethylene glycol)‐co‐poly(trimethylene carbonate) [Poly(PEG‐b‐DTC)] were synthesized. The water‐in‐oil‐in‐water (W/O/W) solvent evaporation technique was adopted to produce anticancer magnetic Poly(PEG‐b‐DTC) microspheres containing tumor necrosis factor‐α (TNF‐α) genes and Fe₃O₄ magnetic ultrafine powder. Drug release studies showed that the microspheres can sustain a steady release rate of TNF‐α genes in 0.1M phosphate buffer saline solution in vitro for up to 60 h. In vitro cytotoxicity assays demonstrated that the microspheres have high inhibition and antitumor action to human hepatocellular carcinoma (Bel‐7204) cells in vitro. In vivo inhibition on the growth of hepatic carcinomas and histopathologic observation indicated that the microspheres possess a markedly high antitumor activity to human hepatocellular carcinoma (Bel‐7204). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A novel thermosensitive triblock copolymer from 100% renewably sourced poly(trimethylene ether) glycol

Bio‐based amphiphilic triblock copolymers with 100% renewably sourced poly(trimethylene ether) glycol (PO3G) as the hydrophobic blocks and statistical copolymer of 2‐(2‐methoxyethoxy)ethyl methacrylate (MEO₂MA) and oligo(ethylene glycol)methacrylate (OEGMA) [P(MEO₂MA‐stat‐OEGMA)] as the hydrophilic blocks are synthesized and characterized. It is found that the molar ratio of MEO₂MA/OEGMA among the resulting copolymers is approximately 70/30. The degree of polymerization (DP) of P(MEO₂MA‐stat‐OEGMA) block ranges from 16 to 90, and the DP of PO3G block is fixed at 35. The amphiphilic copolymers could form core‐shell micelles self‐assembly in aqueous solution at low concentrations, and the micelles are in spherical shape with sizes varying from 121 to 188 nm. With the increasing length of hydrophilic blocks, the critical micelle concentration increases from 2.15 to 13.8 mg L^?1, and the lower critical solution temperature improves from 32.5 to 38.4 °C. The in vitro doxorubicin (DOX) release study shows that all DOX‐loaded micelles have a higher release rate at 37 °C than that at 25 °C. Cytotoxicity test reveals that the blank micelles are nearly nontoxic. These results indicate that the block copolymer micelles containing 100% renewably sourced PO3G can serve as a potential drug delivery carrier. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46112.     

Thermoreversible gelation of a polystyrene–poly(ethylene/butylene)–polystyrene triblock copolymer in n‐octane/4‐methyl‐2‐pentanone solutions

The thermoreversible gelation of a triblock copolymer polystyrene‐block‐poly(ethylene/butylene)‐block‐polystyrene in n‐octane and two solvent mixtures of n‐octane and 4‐methyl‐2‐pentanone with a high n‐octane content has been studied. n‐Octane and 4‐methyl‐2‐pentanone are selective solvents for the middle poly(ethylene/butylene) block and the end polystyrene blocks, respectively. The influence of the solvent composition on the sol–gel transition and the mechanical properties of the gels was studied. The gel formation temperature increased with the copolymer concentration and the n‐octane content in the solvent system. The mechanical properties of the different gels were studied through oscillatory shear measurements. The concentration dependence of the elastic storage modulus showed an exponent close to that expected for gels in good solvents (2.25) that possess a structure similar to those of chemical networks. © 2002 Society of Chemical Industry     

Thermosensitive PMMA core/oligo(ethylene glycol)-based shell microgels as drug carriers in detoxification treatment

The core-shell structured polymer microgels were synthesized by coating the hydrophobic poly(methyl methacrylate) (PMMA) sphere cores with hydrophilic nonlinear poly(ethylene glycol)-based gel shell layer. The uniqueness of these core-shell microgels lies in the integration of the PMMA core microsphere with strong hydrophobicity and the novel oligo(ethylene glycol)-based gel layer with well-defined thermosensitivity for improving loading/release efficacy of two detoxification drugs (chlorpromazine and diltiazem). The hydrophilic shell is composed of hydrophilic copolymer of 2-(2-methoxyethoxy)ethyl methacrylate (MEO₂MA) with oligo(ethylene glycol) methyl ether methacrylates (MEO₅MA). It was found that the molar ratio of two shell monomers n(MEO₂MA)/n(MEO₅MA) of 1:6 was an ideal matching value for production of the P(MEO₂MA)/P(MEO₂MA-co-MEO₅MA) core-shell microgels with tunable volume phase transition temperature and excellent colloidal stability across the physiologically important temperature range. Moreover, chlorpromazine- and diltiazem-loaded microgels can show an obvious thermosensitive release and in vitro sustained-release characteristic up to 80 h.     

Temperature and pH responsive hydrogels based on polyethylene glycol analogues and poly(methacrylic acid) via click chemistry

A novel temperature responsive copolymer, poly[2‐(2‐methoxyethoxy)ethyl methacrylate‐co‐oligo(ethylene glycol)methacrylate‐co‐N‐hydroxymethyl acrylamide] [P(MEO₂MA‐co‐OEGMA‐co‐HMAM)], was synthesized by atom transfer radical polymerization. pH responsive poly(methacrylic acid) (PMAA) was synthesized by reversible addition‐fragmentation chain transfer polymerization. After the hydroxyl groups on P(MEO₂MA‐co‐OEGMA‐co‐HMAM) were transformed into azide groups and the carboxyl groups on PMAA were transformed into alkyne groups respectively, a novel temperature and pH responsive hydrogel was fabricated by click chemistry between the azide‐P(MEO₂MA‐co‐OEGMA‐co‐HMAM) and alkyne‐PMAA in the presence of CuSO₄ and sodium ascorbate in aqueous solution. The rheological kinetics of gel formation demonstrated that gelation had commenced within 5 min at 25 °C, since then the storage modulus (G′) was higher than the loss modulus (G″). SEM images of hydrogel morphology and the swelling ratios of hydrogel at different temperatures and pH proved that the formed hydrogel had temperature and pH sensitivities. Bovine serum albumin was used as a model to evaluate the sustained release of the hydrogel; the results indicated that the hydrogel was a promising candidate for controlling protein drug delivery. © 2015 Society of Chemical Industry     

Synthesis of a biocompatible poly(2‐hydroxyethyl methacrylate)–chitosan core–shell hydrogel latex

Core–shell hydrogel latexes, composed of a poly(2‐hydroxyethyl methacrylate) (PHEMA) core chemically coated with chitosan (CS) shell, were synthesized via an emulsifier‐free emulsion polymerization, free radically initiated by a redox couple of tert‐butyl hydroperoxide and amine groups on CS itself. The variation of some polymerization parameters [e.g., polymerization time, CS/2‐hydroxyethyl methacrylate (HEMA) weight ratio, and content of crosslinker] was systematically investigated in this study. We found that the weight ratios between CS and the HEMA monomer influenced the course of polymerization, which was traced by the change in percentage monomer conversions, and the colloidal stability of the PHEMA–CS hydrogel latexes obtained. Moreover, the polymerization time affected their particle sizes and surface charges. For the colloidally stable PHEMA–CS hydrogel latexes, their sizes and charges ranged from 600 to 689 nm and from 32 to 51 mV, respectively. N,N′‐Methylene bisacrylamide was used as a crosslinking agent for the core component; this was found to be able to enhance the hydrogels' thermal stability and water uptake. Moreover, the 3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5‐diphenyltetrazolium bromide assay showed that 100% cell viability was achieved during the treatment of the PHEMA–CS latex (0.2–2.5 mg/mL) with Caco‐2 cells. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40003.     

Synthesis and characterization of a novel stimuli‐responsive magnetite nanohydrogel based on poly(ethylene glycol) and poly(N‐isopropylacrylamide) as drug carrier

A novel stimuli‐responsive magnetite nanohydrogel (MNHG), namely [poly(ethylene glycol)‐block‐poly(N‐isopropylacrylamide‐co‐maleic anhydride)₂]‐graft‐poly(ethylene glycol)/Fe₃O₄ [PEG‐b‐(PNIPAAm‐co‐PMA)₂]‐g‐PEG/Fe₃O₄, was successfully developed. For this purpose, NIPAAm and MA monomers were block copolymerized onto PEG‐based macroinitiator through atom transfer radical polymerization technique to produce PEG‐b‐(PNIPAAm‐co‐PMA)₂. The synthesized Y‐shaped terpolymer was crosslinked through the esterification of maleic anhydride units using PEG chains to afford a hydrogel. Afterward, magnetite nanoparticles were incorporated into the synthesized hydrogel through the physical interactions. The chemical structures of all synthesized samples were characterized using Fourier transform infrared and proton nuclear magnetic resonance spectroscopies. Morphology, thermal stability, size, and magnetic properties of the synthesized MNHG were investigated. In addition, the doxorubicin hydrochloride loading and encapsulation efficiencies as well as stimuli‐responsive drug release ability of the synthesized MNHG were also evaluated. The drug‐loaded MNHG at physiological condition exhibited negligible drug release values. In contrast, at acidic (pH 5.3) condition and a little bit higher temperature (41 °C) the developed MNHG showed higher drug release values, which qualified it for cancer chemotherapy due to especial physiology of cancerous tissue in comparison with the surrounding normal tissue. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46657.