Synthesis and characteristics of poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive composite hollow latex particles and their application as drug carriers

In this work, the poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive composite hollow latex particles was synthesized by a three‐step reaction. The first step was to synthesize the poly(methyl methacrylate‐co‐methacrylic acid) (poly(MMA‐MAA)) copolymer latex particles by the method of soapless emulsion polymerization. The second step was to polymerize methacrylic acid (MAA), N‐isopropylacrylamide (NIPAAm), and N,N′‐methylenebisacrylamide in the presence of poly(MMA‐MAA) latex particles to form the linear poly(methyl methacrylate‐co‐methacrylic acid)/crosslinking poly(methacrylic acid‐co‐N‐isopropylacrylamide) (poly(MMA‐MAA)/poly(MAA‐NIPAAm)) core–shell latex particles. In the third step, the core–shell latex particles were heated in the presence of ammonia solution to form the crosslinking poly(MAA‐NIPAAm) thermosensitive hollow latex particles. The morphologies of poly(MMA‐MAA)/poly(MAA‐NIPAAm) core–shell latex particles and poly(MAA‐NIPAAm) hollow latex particles were observed. The influences of crosslinking agent and shell composition on the lower critical solution temperature of poly(MMA‐MAA)/poly(MAA‐NIPAAm) core–shell latex particles and poly(MAA‐NIPAAm) hollow latex particles were, respectively, studied. Besides, the poly(MAA‐NIPAAm) thermosensitive hollow latex particles were used as carriers to load with the model drug, caffeine. The effect of various variables on the amount of caffeine loading and the efficiency of caffeine release was investigated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5203–5214     

Synthesis and characterization of new cross-linked terpolymer systems containing silyl group

A series of acrylic terpolymers containing silyl pendant groups was prepared by free radical cross-linking copolymerization. Me₃Si, Et₃Si and t-BuMe₂Si together with cubane-1, 4-dicarboxylic acid (CDA) were covalently linked with 2-hydroxyethyl methacrylate (HEMA). The silyl-linked HEMA are abbreviated as TMSiEMA, TESiEMA and TBSiEMA respectively. Cubane-1, 4-dicarboxylic acid (CDA) linked to two HEMA group is the cross-linking agent (CA). Free radical cross-linking terpolymerization of the methyl methacrylate (MMA) and methacrylic acid (MAA) with two different molar ratios of organosilyl monomers and CA was carried out at 60–70 ^∘C. The compositions of the cross-linked three-dimensional polymers were determined by FT-IR spectroscopy. The glass transition temperature (Tg) of the network polymers was determined calorimetrically. The Tg of network terpolymers increases with increasing of cross-linking degree. Equilibrium swelling studies were carried out in enzyme-free simulated gastric and intestinal fluids (SGF and SIF, respectively). The gels swelled more in SIF than in SGF. The swelling behaviour of the copolymers was dependent on the content of MAA groups and caused a decrease in gel swelling in pH 1 or an increase in gel swelling in pH 7.4. Based on the great difference in swelling ratio at pH 1 and 7.4 for P-1, P-6 and P-10 appear to be good candidates for colon-specific drug delivery.     

Synthesis and characteristics of poly(methyl methacrylate‐co‐methacrylic acid)/poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive semi‐hollow latex particles and their application to drug carriers

In this work, the poly(methyl methacrylate‐co‐methacrylic acid)/poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive composite semi‐hollow latex particles was synthesized by three processes. The first process was to synthesize the poly(methyl methacrylate‐co‐methacrylic acid) (poly (MMA‐MAA)) copolymer latex particles by the method of soapless emulsion polymerization. The second process was to polymerize methacrylic acid (MAA), N‐isopropylacrylamide (NIPAAm), and crosslinking agent, N,N′‐methylenebisacrylamide, in the presence of poly(MMA‐MAA) latex particles to form the linear poly(methyl methacrylate‐co‐methacrylic acid)/crosslinking poly(methacrylic acid‐co‐N‐isopropylacrylamide) (poly(MMA‐MAA)/poly(MAA‐NIPAAm)) core–shell latex particles with solid structure. In the third process, part of the linear poly(MMA‐MAA) core of core–shell latex particles was dissolved by ammonia to form the poly(MMA‐MAA)/poly(MAA‐NIPAAm) thermosensitive semi‐hollow latex particles. The morphologies of the semi‐hollow latex particles show that there is a hollow zone between the linear poly(MMA‐MAA) core and the crosslinked poly(MAA‐NIPAAm) shell. The crosslinking agent and shell composition significantly influenced the lower critical solution temperature of poly(MMA‐MAA)/poly(MAA‐NIPAAm) semi‐hollow latex particles. Besides, the poly(MMA‐MAA)/poly(MAA‐NIPAAm) thermosensitive semi‐hollow latex particles were used as carriers to load with the model drug, caffeine. The processes of caffeine loaded into the semi‐hollow latex particles appeared four situations, which was different from that of solid latex particles. In addition, the phenomenon of caffeine released from the semi‐hollow latex particles was obviously different from that of solid latex particles. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3441–3451     

Synthesis and properties of biodegradable thermo- and pH-sensitive poly[(N-isopropylacrylamide)-co-(methacrylic acid)] hydrogels

Thermo- and pH-sensitive hydrogels were synthesized via the copolymerization of N-isopropylacrylamide (NIPAAm) and methacrylic acid (MAA) crosslinked with a biodegradable PEG-co-PCL macromolecular crosslinker under UV irradiation. Swelling measurements showed that temperature and pH sensitivity of the resultant hydrogels were highly dependent on the composition of the hydrogels as well as temperature and pH of the local medium. The pH and temperature dependence of the hydrogels displayed good reversibility. The hydrolytic degradation studies showed that the degradation rate of the hydrogels increased with the increasing content of MAA introduced in the hydrogels in pH 7.4 PBS solutions at 37 °C. The study on the release of BSA indicated that the release rate of BSA was higher at pH 7.4 than at pH 2.0, and increased with the increase of the MAA content in the hydrogels in pH 7.4 PBS solutions at 37 °C. These hydrogel materials are desirable for potential applications as smart drug delivery systems.     

Synthesis and characterization of biodegradable pH-sensitive hydrogels based on poly(?-caprolactone), methacrylic acid, and poly(ethylene glycol)

In this work, a novel biodegradable pH-sensitive hydrogel based on poly(?-caprolactone) (PCL), methoxpoly(ethylene glycol) (MPEG) and methacrylic acid (MAA) was prepared by UV-initiated free radical polymerization. The resulting macromonomers and hydrogels were characterized by FTIR and/or ¹H NMR. Swelling behaviour and pH sensitivity of the hydrogels were studied in detail. With increase in pH of aqueous medium from 1.2 to 7.2, swelling ratio of the hydrogels increased accordingly. The hydrolytic degradation behaviour was also investigated. The prepared biodegradable pH-sensitive hydrogel based on PCL, MPEG, and MAA might have great potential application in smart drug delivery system.     

Microstructural Characterization of Diblock Copolymers Formed by Styrene and Different Methacrylic Units

FT-IR, DSC, and NMR techniques allowed the structural characterization of four copolymers formed by styrene and methacrylic units (methacrylic acid (MAA), dimethylamine ethyl methacrylate (DMAEMA), sodium methacrylate (MANa), and 1-hydroxyethyl methacrylate (HEMA). The copolymer composition was studied by Fourier transform-infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. The thermal behavior of the block copolymers was analyzed by differential scanning calorimetry (DSC). Three of the four copolymers showed two transitions caused by changes in the polymer heat capacity (ΔCp) of each block. Diffusion-ordered spectroscopy (DOSY) experiments were used to distinguish copolymer from homopolymer mixtures. Finally, the triad-level stereosequences of styrene-methacrylic copolymers were obtained using ¹³C NMR. The results indicate that by increasing the alkyl-substituent length in the methacrylic block, the probability of syndiotactic polymerization increases.     

Enhancement of visible light-induced gelation of photocurable gelatin by addition of polymeric amine

We evaluated the effect of an electron donor on photogelation of photocurable gelatin, which is gelatin partially derivatized with eosin (eosin–gelatin). As an electron donor, ascorbic acid, 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA), and three kinds of radical polymerized amines such as poly(N,N-dimethylacrylamide-co-2-(N,N-dimethylamino)ethyl methacrylate) (poly(DMAAm-co-DMAEMA)), poly(N,N-dimethylacrylamide-co-3-(N,N-dimethylamino)propyl acrylamide) (poly(DMAAm-co-DMAPAAm)), and poly(3-(N,N-dimethylamino)propyl acrylamide) (polyDMAPAAm) were examined. Upon photo irradiation at the wavelength ranging from 400 to 520 nm with low illumination intensity (7.7 × 10³ lx), no gel was obtained from 20 wt.% of a viscous aqueous solution of the eosin–gelatin even by adding with ascorbic acid. Whereas in the presence of monomeric amine (DMAEMA, 3.0 wt.%), gel formation occurred by radical recombination between eosin groups incorporated into the gelatin. When the polymeric amines were added to the eosin–gelatin solution, gelation was markedly enhanced due to cross-linking of gelatins through polymeric amines in addition to direct bonding between gelatins. An increase in amine unit content in the polymeric amines resulted in increased gel yield and reduced swelling degree of water. In the presence of polyDMAPAAm, almost all gelatins were converted relatively rigid hydrogel. Application for a topical hemostatic glue was preliminary performed in rat injured model. A rat liver injured in laparotomy was coated with the aqueous eosin–gelatin solution containing polyDMAPAAm. Upon irradiation, the solution was immediately converted to a swollen gel, which was tightly adhered to the liver tissue and concomitantly hemostasis was completed with little tissue damage.     

Synthesis of low-molecular-weight copolymers of N-vinylpyrrolidone with 2-hydroxyethyl methacrylate and of polymeric oxacillin esters derived from them

The radical copolymerization of N-vinylpyrrolidone with 2-hydroxyethyl methacrylate in 2-propanol at 60°C, initiated by azobis(isobutyronitrile) and inhibited by mercaptoethanol or terminated after a short period, was studied. The low-molecular-weight copolymers obtained were used to prepare new polymeric forms of Oxacillin antibiotic. The chemical uniformity, composition, and antimicrobial activity of the new derivatives were studied, and the rate of their hydrolysis in saline (pH 7.3) and glycine buffer (pH 2.0) was determined.     

Stabilization of glucose oxidase fromPenicillium vitale entrapped in high-concentration gels

Glucose ixidase fromPenicillium vitale was immobilized in a 2-hydroxyethyl methacrylate (HEMA) gel containing 0.3 to 2% of methacrylic acid (MAA) or MAA neutralized by allylamine (AA). Depending on the MAA quantity of MAA in the gel, the thermal irreversible inactivation(k _in) constants of the immobilized enzymes sharply decrease at gel concentrations higher than 29 to 50% at pH 5.8. A 220- to 250-fold decrease ofk _in was observed in 60 to 80% gel. The inactivation rate of enzyme in HEMA gel also decreases considerably under the action of urea. Over the range of pH 5.0 to 9.0 thek _in of the native enzyme depends on pH by a degree of 2.1, and of the immobilized enzyme, 0.3 to 0.55. Over the pH range of 5.2 to 5.7,k _in of the native and immobilized enzymes are approximate, whereas at pH 8 and over the difference betweenk _in values exceeds four orders of magnitude. The activity dependence of the immobilized enzyme on pH is shifted two units to the alkaline region. This shift depends on the ionic strength of the solution. This dependence is best reflected in the high gel concentrations. A mechanism of enzymes stabilization in the concentrated HEMA gel is discussed.     

Microgels containing methacrylic acid: effects of composition on pH-triggered swelling and gelation behaviours

pH-responsive microgels are cross-linked polymer colloids that swell when the pH approaches the pK _a of the particles. In this work, we present a comprehensive investigation of pH-triggered particle swelling and gel formation for a range of microgels containing methacrylic acid (MAA). The microgels investigated have the general composition poly(A/MAA/X), where A and X are the primary co-monomer and cross-linking monomer, respectively. The primary co-monomers were methyl methacrylate (MMA), ethyl acrylate (EA) or butyl methacrylate. The cross-linking monomers were either butanediol diacrylate (BDDA) or ethyleneglycol dimethacrylate (EGDMA). The microgels were studied using scanning electron microscopy, photon correlation spectroscopy (PCS) and dynamic rheology measurements. Gel phase diagrams were also constructed. The particles swelled significantly at pH values greater than approximately 6.0. It was shown that poly(EA/MAA/X) microgels swelled more strongly than poly(MMA/MAA/X) microgels. Furthermore, greater swelling occurred for particles prepared using EGDMA than BDDA. Concentrated dispersions of all the microgels studied exhibited pH-triggered gel formation. It was found that the fluid-to-gel transitions for the majority of the six microgel dispersions investigated could be explained using PCS data. In those cases, gelation was attributed to a colloidal glass transition. Interestingly, the microgels that were considered to have the highest hydrophobic content gelation occurred under conditions where little particle swelling was evident from PCS. The data presented show that gelled poly(EA/MAA/BDDA) and poly(MMA/MAA/EGDMA) microgel dispersions have the strongest elasticities at pH = 7.     

Amphiphilic conetworks. IV. Poly(methacrylic acid)‐l‐polyisobutylene and poly(acrylic acid)‐l‐polyisobutylene based hydrogels prepared by two‐step polymer procedure. New pH responsive conetworks

This article describes the synthesis and characterization of new amphiphilic polymer conetworks containing hydrophilic poly(methacrylic acid) (PMAA) or poly(acrylic acid) (PAA) and hydrophobic polyisobutylene (PIB) chains. These conetworks were prepared by a two‐step polymer synthesis. In the first step, a cationic copolymer of isobutylene (IB) and 3‐isopropenyl‐α,α‐dimethylbenzyl isocyanate (IDI) was prepared. The isocyanate groups of the IB–IDI random copolymer were subsequently transformed in situ to methacrylate (MA) groups in reaction with 2‐hydroxyethyl methacrylate (HEMA). In the second step, the resulting MA‐multifunctional PIB‐based crosslinker, PIB(MA)_n, with an average functionality of approximately four methacrylic groups per chain, was copolymerized with methacrylic acid (MAA) or acrylic acid (AA) by radical mechanism in tetrahydrofuran giving rise to amphiphilic conetworks containing 31–79 mol % of MAA or 26–36 mol % of AA. The synthesized conetworks were characterized with solid‐state ¹³C‐NMR spectroscopy and differential scanning calorimetry. The amphiphilic nature of the conetworks was proven by swelling in both aqueous media with low and high pH and n‐heptane. The effect of varying pH on the swelling behavior of the synthesized conetworks is presented. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1284–1291, 2009     

Synthesis and characterization of two new cyclobutyl and aryl hydroxyethyl methacrylate monomers and their polymers

Two new hydroxyethyl methacrylates having aryl and cyclobutane rings were synthesized by addition to 1-(epoxyethyl)-3-aryl-3-methylcyclobutane to methacrylic acid. The monomers prepared are 2-(3-methyl-3-phenylcyclobutyl)-2-hydroxyethyl methacrylate (PCHEMA) and 2-(3-methyl-3-mesitylcyclobutyl)-2-hydroxyethyl methacrylate (MCHEMA). Both monomers were polymerized at 60°C in 1,4-dioxane solution using benzoyl peroxide as initiator. Poly(PCHEMA) and poly(MCHEMA) and their monomers were characterized by FT-IR and ¹H- and ¹³C-NMR techniques. Weight average molecular weights of the polymers were determined for poly(PCHEMA) poly(MCHEMA) by gel permation chromatography. Thermal stabilities of the polymers were essentially the same. Glass transition temperatures for poly(PCHEMA) and poly(MCHEMA) were determined as 105 and 137°C, respectively. No changes of the polymers by irradiation with UV light at 254 nm were observed. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2123–2128, 1997     

pH响应型P(HEMA/MAA)纳米微凝胶分散液的凝胶化行为和流变性能

制备了在修复受损组织方面有应用潜能的纳米级聚(甲基丙烯酸羟乙酯/甲基丙烯酸) (P(HEMA/MAA))微凝胶; 采用试管倒转法对不同pH值和浓度的P(HEMA/MAA)微凝胶分散液的凝胶化相转变行为进行了研究; 借助椎板流变仪考察了低浓度和高浓度微凝胶分散液的流变性能, 并对pH触发物理凝胶化相转变机理进行了推测. 结果表明: 在生理pH值环境下, 一定浓度的P(HEMA/MAA)微凝胶分散液可以发生凝胶化相转变形成凝胶态, pH=7时, HEMA/MAA进料摩尔比为8/2的微凝胶分散液凝胶化后得到的凝胶力学性能最佳, 最大弹性模量(G')可达7.58×10³ Pa; P(HEMA/MAA)微凝胶颗粒在不同条件下具有不同的溶胀效果, 导致低浓度分散液的表观粘度发生相应的变化, 并由此推测出微凝胶颗粒的溶胀过程由外及内, 分为三个阶段; 高浓度微凝胶分散液发生凝胶化相转变主要是由颗粒间或颗粒与分散介质间形成的空间静电稳定作用和氢键共同作用引起的.     

Synthesis and mechanistic investigations of pH-responsive cationic poly(aminoester)s

The synthesis and degradation mechanisms of a class of pH-sensitive, rapidly degrading cationic poly(α-aminoester)s are described. These reactive, cationic polymers are stable at low pH in water, but undergo a fast and selective degradation at higher pH to liberate neutral diketopiperazines. Related materials incorporating oligo(α-amino ester)s have been shown to be effective gene delivery agents, as the charge-altering degradative behavior facilitates the delivery and release of mRNA and other nucleic acids in vitro and in vivo. Herein, we report detailed studies of the structural and environmental factors that lead to these rapid and selective degradation processes in aqueous buffers. At neutral pH, poly(α-aminoester)s derived from N-hydroxyethylglycine degrade selectively by a mechanism involving sequential 1,5- and 1,6-O→N acyl shifts to generate bis(N-hydroxyethyl) diketopiperazine. A family of structurally related cationic poly(aminoester)s was generated to study the structural influences on the degradation mechanism, product distribution, and pH dependence of the rate of degradation. The kinetics and mechanism of the pH-induced degradations were investigated by ¹H NMR, model reactions, and kinetic simulations. These results indicate that polyesters bearing α-ammonium groups and appropriately positioned N-hydroxyethyl substituents are readily cleaved (by intramolecular attack) or hydrolyzed, representing dynamic “dual function” materials that are initially polycationic and transform with changing environment to neutral products.

The synthesis and degradation mechanisms of a class of pH-sensitive, rapidly degrading cationic poly(α-aminoester)s are described.     

Hairy polymeric nanocapsules with ph‐responsive shell and thermoresponsive brushes: Tunable permeability for controlled release of water‐soluble drugs

The hairy poly(methacrylic acid‐co‐divinylbenzene)‐g‐poly(N‐isopropylacrylamide) (P(MAA‐co‐DVB)‐g‐PNIPAm) nanocapsules with pH‐responsive P(MAA‐co‐DVB) inner shell and temperature‐responsive PNIPAm brushes were prepared by combined distillation–precipitation copolymerization and surface thiol‐ene click grafting reaction using 3‐(trimethoxysilyl)propyl methacrylate‐modified silica (SiO₂‐MPS) nanospheres as a sacrificial core material. The well‐defined PNIPAm was synthesized by a reversible addition fragmentation chain transfer (RAFT) polymerization. The chain end was converted to a thiol by chemical reduction. The PNIPAm was integrated into the nanocapsules via thiol‐ene click reaction. The surface thiol‐ene click reaction conduced to tunable grafting density of PNIPAm brushes. The grafting densities decreased from 0.70 chains nm^?2 to 0.15 chains nm^?2 with increasing the molecular weight of grafted PNIPAm chains. Using water soluble doxorubicin hydrochloride (DOX·HCl) as a model molecular, the tunable shell permeability of the nanocapsule was investigated in detail. The permeability constant can be tuned by controlling the thickness of the P(MAA‐co‐DVB) inner shell, the grafting density of PNIPAm brushes, and the environmental pH and temperature. The tunable shell permeability of these nanocapsules results in the release of the loaded guest molecules with manipulable releasing kinetics. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2202–2216     

Preparation of a novel pH-responsive silver nanoparticle/poly(HEMA-PEGMA-MAA) composite hydrogel

In this paper, series of novel pH-responsive silver (Ag) nanoparticle/poly(2-hydroxyethyl methacrylate (HEMA)-poly(ethylene glycol) methyl ether methacrylate (PEGMA)-methacrylic acid (MAA)) composite hydrogel were successfully prepared by in situ reducing Ag⁺ ions anchored in the hydrogel by the deprotonized carboxyl acid groups. X-ray diffraction (XRD), UV-vis spectrophotometry, transmission electron microscopy (TEM) and electric conductivity tests were used to characterize the composite system. It was found that the size and morphology of the reduced Ag nanoparticles in the composite hydrogels could be changed by loading the Ag⁺ ions at various swelling ratios of hydrogel. Moreover, compared to the pure poly(HEMA-PEGMA-MAA) hydrogel, not only did the Ag nanoparticle/poly(HEMA-PEGMA-MAA) composite hydrogels exhibit much higher swelling ratio and faster deswelling rate, but also higher pH switchable electrical properties upon controlling the interparticle distance under pH stimulus. The pH responsive nanocomposite hydrogel reported here might be a potentially smart material in the range of applications including electronics, biosensors and drug-delivery devices.     

Amphiphilic polymeric micelle as pseudostationary phase in electrokinetic chromatography for analysis of eight corticosteroids in cosmetics

Amphiphilic polymeric micelle, as a novel pseudostationary phase in EKC was used to determine eight kinds of corticosteroids namely hydrocortisone, prednisolone, hydrocortisone acetate, prednisone, cortisone acetate, prednisolone acetate, dexamethasone, and triamcinolone acetonide in cosmetics. Amphiphilic random copolymer poly(methyl methacrylate‐co‐methacrylic acid) (P(MMA‐co‐MAA)) was micellizated via neutralization in alkaline aqueous solution. The influences of the molar ratio of monomer MMA to MAA, the concentration of polymer and pH on the polymeric micelle microstructure and EKC performances were investigated. As molar ratio of MMA to MAA in P(MMA‐co‐MAA) increased, both CMC and environmental polarity of the inner core in polymeric micelle decreased dramatically. With increasing monomer ratio, the size of polymeric micelles increased firstly, and then decreased, finally increased again. ζ potential of the micelle had a slight decline trend. As increment of polymer concentration, the size of the polymeric micelle increased steadily. By optimizing the monomer ratio, the polymer concentration, and pH of the running buffer, as well as operation conditions such as separation voltage and temperature, the eight analytes could be separated within 16.5 min using 7.5 mg/mL polymer with the monomer ratio of 7:3 dissolved in pH 9.2 borax buffer as the running buffer. The method has been used for analysis of corticosteroids in cosmetic samples with simple extraction; the recoveries for eight analytes were between 85.9 and 106%. This method was of accuracy, repeatability, pretreatment simplicity, and could be applied to the quality control of cosmetics.     

Synthesis and characterization of poly(2‐ethylhexyl methacrylate) copolymers containing pendant,self‐complementary multiple‐hydrogen‐bonding sites

The synthesis and characterization of copolymers containing 2‐ethylhexyl methacrylate and a quadruple‐hydrogen‐bonding site, 2‐ureido‐4[1H]‐pyrimidone methacrylate (UPyMA), are described. An analogous dimeric hydrogen‐bond‐containing copolymer based on 2‐ethylhexyl methacrylate and methacrylic acid (PEHMA‐co‐MAA) was also synthesized for comparative purposes. The glass‐transition temperatures of the poly(2‐ethylhexyl methacrylate‐co‐2‐ureido‐4[1H]‐pyrimidone methacrylate) (PEHMA‐co‐UPyMA) series increased linearly with increasing UPyMA content. Creep compliance measurements as a function of temperature indicated a decrease in the creep compliance with increasing UPyMA content over the range of 1–10 mol % UPyMA. Melt rheological analysis also showed an increase and lengthening of the plateau modulus as a function of frequency with increasing UPyMA content, as well as increasing complex viscosity as a function of temperature. The analogous PEHMA‐co‐MAA copolymer, which contained 11 mol % methacrylic acid, showed, in the melt rheological analysis, behavior similar to that of the PEHMA‐co‐UPyMA copolymer containing only 1 mol % UPyMA units. The multiple‐hydrogen‐bond‐containing copolymers were successfully analyzed with time–temperature superposition for the construction of master curves. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4618–4631, 2005     

Amphiphilic poly(N,N-dimethylamino-2-ethyl methacrylate)-g-poly(ε-caprolactone) graft copolymers: synthesis and characterisation

Amphiphilic poly(N,N-dimethylamino-2-ethyl methacrylate)-g-poly(ε-caprolactone) graft copolymers (PDMAEMA-g-PCL) with various compositions and molecular weights were synthesised via a fully controlled three-step strategy. First, poly(ε-caprolactone) macromonomers (PCLMA) were prepared by ring-opening polymerization (ROP) of ε-caprolactone (CL) initiated by aluminum triisopropoxide (Al(OⁱPr)₃), followed in a second step by quantitative esterification of PCL hydroxy end-groups with a methacrylic acid derivative. Finally, the controlled copolymerization of PCLMA and N,N-dimethylamino-2-ethyl methacrylate (DMAEMA) was carried out by atom transfer radical polymerisation (ATRP) in THF at 60 °C using CuBr ligated with 1,1,4,7,10,10, hexamethyl triethylenetetramine and ethyl 2-bromoisobutyrate as catalyst and initiator, respectively. Furthermore, PDMAEMA-g-PCL graft copolymers were reacted with methyl iodide to convert the pendant tertiary amines into quaternary ammonium iodides increasing accordingly their water solubility. Some preliminary experiments was further carried out by tensiometry and dynamic light scattering in order to shed so light on the tensioactive behaviour of these amphiphilic graft copolymers (with protonated amines or quaternary ammonium cations).     

Formation of Fe2+-phenanthroline complexes in the volume of hydrogel

The interaction of weakly crosslinked gels of poly(methacrylic acid) and a nonionic gel based on N-vinylcaprolactam and N-vinylimidazole with Fe²⁺ ions in aqueous solutions has been studied. A comparative study of the conformational state and of the absorption ability of the gels for their interaction with iron and ferroin ions has been performed. It has been shown that Fe²⁺ ions are efficiently absorbed by both poly(methacrylic acid) gels and the gels based on N-vinylcaprolactam and N-vinylimidazole. In this case, the poly(methacrylic acid) gels undergo contraction, while nonionic gels derived from N-vinylcaprolactam and N-vinylimidazole experience swelling. During the interaction of gels containing immobilized Fe²⁺ ions with phenanthroline, the efficient absorption of the complexon and the formation of Fe²⁺-phenanthroline complexes in the gel volume take place, thus inducing the contraction of gels. The interaction of poly(methacrylic acid) gels with ferroin is accompanied by the absorption of the complex, the formation of the tertiary complexes, and the collapse of the gel. The efficiency of formation of tertiary complexes in the gel volume is independent of their preparation procedure.