Water affinity and permeability in membranes of alginate-Ca2+ containing poly(n-isopropylacrylamide)

Hydrogels based on semi-interpenetrating network (semi-IPN) combining alginate-Ca²⁺ (matrix) with poly(N-isopropyl acrylamide) (PNIPAAm) were prepared and characterized in order to determine their affinity to water and their permeability to orange II as a function of temperature. Membranes of these hydrogels were obtained by gelation of the aqueous solution of alginate and PNIPAAm by the addition of CaCl₂. The presence of PNIPAAm chains inside the hydrogels alters the water affinity when compared to the pure alginate-Ca²⁺ hydrogels. Although the water uptake capability decreases above 32 °C (Low Critical Solution Temperature (LCST) of PNIPAAm in water), no shrinking of the semi-IPN hydrogels during the phase separation of the PNIPAAm was observed. The permeability of orange II as a function of temperature decreases at 32 °C and shows a dependence on the molar mass of the alginate. The partition coefficient of orange II in the hydrogel membrane, relative to water, decreases by increasing the temperature and its permeability follows a similar behavior. It was proposed that above the LCST of PNIPAAm the Alginate-Ca²⁺ networks mechanically support the collapsed PNIPAAm chains and the diffusion of orange II is minimized. The collapsing process may be followed by the formation of a complex between the carboxylic side groups of alginate and –NH–R groups of PNIPAAm. It would expose the isopropyl groups of PNIPAAm chains, providing a hydrophobic environment that minimizes the interaction between the dye and the polymeric matrix.     

Uranyl ion uptake capacity of poly (N-isopropylacrylamide/maleic acid) copolymeric hydrogels prepared by gamma rays

The effect of gel composition, absorbed dose and pH of the solution on the uranyl ion uptake capacity of N-isopropylacrylamide/maleic acid copolymeric hydrogels containing 0–3 mol% of maleic acid at 48 kGy have been investigated. Uranyl uptake capacity of hydrogels are found to increase from 18.5 to 94.8 mg [UO₂²⁺]/g dry gel as the mole % of maleic acid content in the gel structure increased from 0 to 3. The percent swelling, equilibrium swelling and diffusion coefficient values have been evaluated for poly(N-isopropylacrylamide/maleic acid) hydrogels at 500 ppm of uranyl nitrate solution.     

Temperature-responsive photoluminescence of quinoline-labeled poly(N-isopropylacrylamide) in aqueous solution

The pH- and temperature-responsive optical properties of a quinoline-labeled poly(N-isopropylacrylamide) copolymer are explored in aqueous solution and compared to the respective behavior of a similar quinoline-labeled poly(N,N-dimethylacrylamide) copolymer. These copolymers, P(NIPAM-co-SDPQ) and P(DMAM-co-SDPQ), were prepared through free radical copolymerization of 2,4-diphenyl-6-(4-vinylphenyl)quinoline (SDPQ) with the thermosensitive N-isopropylacrylamide (NIPAM) and the hydrophilic N,N-dimethylacrylamide (DMAM), respectively. Both copolymers exhibit the well-known pH-controlled optical response of quinoline unit in aqueous solution and the emitted color changes from blue to green upon decreasing pH. Nevertheless, a ～20 nm emission shift is observed upon heating the aqueous P(NIPAM-co-SDPQ) solution, regardless of pH, due to the formation of hydrophobic microdomains (Nile Red probing), as a consequence of the Lower Critical Solution Temperature (LCST) behavior of this copolymer in water. Interestingly, this LCST behavior also imposes the partial deprotonation of the otherwise protonated SDPQ unit at pH = 2 and the emission of the basic form appears upon increasing temperature, suggesting that the acid/base equilibrium of the quinoline unit is significantly temperature-controlled, when introduced in the thermosensitive poly(N-isopropylacrylamide) chain.     

Adsorption of Apollo reactive dyes on poly(N,N dimethylamino ethylmethacrylate) hydrogels

Poly(N,N-dimethylamino ethylmethacrylate) [P(DMAEMA)] hydrogels were prepared by irradiating the ternary mixtures of dimethylamino ethylmethacrylate (DMAEMA)/ethyleneglycol dimethacrylate (EGDMA)/water (H₂O) by γ-rays at ambient temperature. The swelling of four types of DMAEMA hydrogels in distilled water is higher than the swelling of these hydrogels in dye solutions. The value of equilibrium swelling of P(DMAEMA)1 hydrogel was 338% at pH 7.0 in distilled water, while it was 325% and 326% at pH 7.0 in Apollofix Red (AR) and Apollofix Yellow (AY) solutions, respectively. The adsorption capacity of P(DMAEMA)1 hydrogel was found to increase from 85 to 131 mg for AR g⁻¹ dry gel and from 58 to 111 mg for AY g⁻¹ dry gel with decreasing pH of the dye solutions.     

Swelling and thermodynamic studies of temperature responsive 2-hydroxyethyl methacrylate/itaconic acid copolymeric hydrogels prepared via gamma radiation

The copolymeric hydrogels based on 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) were synthesized by gamma radiation induced radical polymerization. Swelling and thermodynamic properties of PHEMA and copolymeric P(HEMA/IA) hydrogels with different IA contents (2, 3.5 and 5 mol%) were studied in a wide pH and temperature range. Initial studies of so-prepared hydrogels show interesting pH and temperature sensitivity in swelling and drug release behavior. Special attention was devoted to temperature investigations around physiological temperature (37 °C), where small changes in temperature significantly influence swelling and drug release of these hydrogels. Due to maximum swelling of hydrogels around 40 °C, the P(HEMA/IA) hydrogel containing 5 mol% of IA without and with drug-antibiotic (gentamicin) were investigated at pH 7.40 and in the temperature range 25–42 °C, in order to evaluate their potential for medical applications.     

Adsorption of methyl violet in aqueous solutions by poly(N-vinylpyrrolidone-co-methacrylic acid) hydrogels

N-vinylpyrrolidone(VP)/methacrylic acid (MAA) monomer mixtures containing different quantities of methacrylic acid were irradiated with gamma-radiation to form hydrogels. Mixtures which contain 5, 10, 15% and irradiated with 3.4 kGy were used for swelling and diffusion studies in water and solutions of methyl violet and for the adsorption of methyl violet from aqueous solutions. Diffusion of water and methyl violet within hydrogels were found to be of non-Fickian character. In the dye adsorption experiments, the effects of pH, concentration of aqueous solution of dye and the composition of hydrogels on the adsorption process were investigated. When the pH and concentration of aqueous solutions of dye and the MAA content in hydrogels increased, the adsorption increased.     

Thermogelling polymers composed of poly(cyclohexylenedimethylene adipate) and poly(ethylene glycol)

Block copolymers composed of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic biodegradable polyesters have been reported as thermogelling polymers, because they feature temperature-dependent sol-to-gel or gel-to-sol transitions in aqueous solutions. In this study, a series of thermogelling poly(ethylene glycol methyl ether)-block–poly(cyclohexylenedimethylene adipate)-block–poly(ethylene glycol methyl ether) triblock copolymers and PEG-block–poly(cyclohexylenedimethylene adipate) multiblock copolymers was synthesized by reacting hydroxyl-terminated poly(cyclohexylenedimethylene adipate) (PCA) with poly(ethylene glycol methyl ether) and PEG, respectively, using 1,6-diisocyanatohexane as the coupling agent. Two hydroxyl-terminated PCAs, i.e., poly(1,4-cyclohexylenedimethylene adipate) and poly(1,3/1,4-cyclohexylenedimethylene adipate), were synthesized by the condensation reaction of adipic acid (AA) with 1,4-cyclohexanedimethanol (CHDM) and 1,3/1,4-CHDM, respectively, and used as the hydrophobic polyester blocks of these thermogelling copolymers to compare the effect of crystallinity on the sol-to-gel transition behavior.The polymers were characterized using proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, solubility testing, and rheological analysis. Experimental results revealed that the structure of the PCA block (crystalline vs. amorphous), the molecular weights of the hydrophobic PCA and hydrophilic PEG blocks, and the type of thermogelling polymer (triblock vs. multiblock) influenced the solubility, polymer micelle packing characteristics, maximum storage modulus, and sol-to-gel temperature of the polymers. Among all the samples at 40 wt.% aqueous solutions, triblock copolymer TB3 showed sol-to-gel temperature at 22 °C, and had the highest maximum storage modulus about 170 Pa.     

Thermal and FTIR analysis of the miscibility and phase behaviour of poly (isobutyl methacrylate-co-4-vinylpyridine)/poly (styrene-co-acrylic acid) systems

The miscibility and phase behaviour of poly (isobutyl methacrylate-co-4-vinylpyridine) containing 20 mol% of 4-vinylpyridine (IBM4VP20) and poly (styrene-co-acrylic acid) containing 27 or 32 mol% of acrylic acid (SAA27 or SAA32) mixtures were investigated by DSC, TGA and FTIR spectroscopy in the 25–180 °C temperature range. The results showed that sufficient specific carboxyl–pyridine hydrogen bonding interactions occurred between these copolymers and led to miscible blends as cast from THF and to inter-polymer complexes of significantly improved thermal stability when butan-2-one is the common solvent. The self-association effect on the inter-polymer interactions was evidenced by the decrease of complexation yields, observed when the carboxylic content is increased above 27 mol% as with SAA32.The trend of phase behaviour predicted by a thermodynamic analysis of the specific interactions of hydrogen bonding type that occurred between the two components of the SAA27/IBM4VP20 blends, neglecting the weak carboxyl–ester interactions and the functional group accessibility effect, carried out using the Painter–Coleman association model that considers the screening effects, is in a fair agreement with the experimental results. Moreover an LCST is predicted to occur at relatively high temperature.     

Poly(ether amine) and cross-linked poly(propylene oxide) diacrylate thin-film polymer electrolyte for 3D-microbatteries

This paper presents a novel thin-film electrolyte of a 2:1 blend of polyetheramine (glyceryl poly(oxypropylene)) and cross-linked oligomeric poly(propylene oxide) diacrylate with LiTFSI. The polyetheramine acts as a surfactant, and can thereby be applied as a conformal coating on complex surfaces—here demonstrated for porous LiFePO₄ cathodes—making it useful for 3D-microbatteries. The poly(propylene oxide) diacrylate blends with the surfactant and is easily UV cross-linked, thereby ensuring good mechanical stability. Electrolytes, ~ 2 μm thick, were casted onto LiFePO₄ cathodes and cycled against metallic lithium, displaying stable discharge capacities of ~ 8 mAh/g at room temperature and ~ 120 mAh/g at 60 °C. The electrolyte showed conductivities of 3.45 × 10^? 6 and 5.80 × 10^? 5 S cm^? 1 at room temperature and 60 °C, respectively.     

Gamma radiation synthesis of comb-type graft hydrogels based on poly(acrylic acid) and 4-vinylpyridine

A pH-sensitive comb-type hydrogel was obtained by gamma radiation polymerization and crosslinking of acrylic acid (AAc) in solution. The pH-sensitive 4-vinylpyridine (4VP) was then grafted to the poly acrylic acid (PAAc) hydrogel using gamma radiation from a ⁶⁰Co source. The comb type graft polymers obtained (net-PAAc)-g-4VP has been studied through determination of graft yield and swelling behavior. The critical pH value was found to be 5.6. The apparent mechanical properties appear to be qualitatively better than hydrogels of PAAc upon swelling. The new comb-type system presents faster swelling response (30 h) than the polyacrylic acid hydrogel (50 h). The increase in dose rate from 7.3 to 11.3 kGy h⁻¹, increase the radiation grafting percentage of 4VP in the system. Comb-type polymers were also characterized by DSC, TGA and FTIR-ATR.     

Synthesis and characterization of Poly(N-isopropylacrylamide)/Poly(acrylic acid) semi-IPN nanocomposite microgels

A novel pH- and temperature-sensitive nanocomposite microgel based on linear Poly(acrylic acid) (PAAc) and Poly(N-isopropylacrylamide) (PNIPA) crosslinked by inorganic clay was synthesized by a two-step method. First, PNIPA microgel was prepared via surfactant-free emulsion polymerization by using inorganic clay as a crosslinker, and then AAc monomer was polymerized within the PNIPA microgel. The structure and morphology of the microgel were confirmed by FTIR, WXRD and TEM. The results indicated that the exfoliated clay platelets were dispersed homogeneously in the PNIPA microgels and acted as a multifunctional crosslinker, while the linear PAAc polymer chains incorporated in the PNIPA microgel network to form a semi-interpenetrating polymer network (semi-IPN) structure. The hydrodynamic diameters of the semi-IPN microgels ranged from 360 to 400 nm, which was much smaller than that of the conventional microgel prepared by using N,N′-methylenebis(acrylamide) (MBA) as a chemical crosslinker, the later was about 740 nm. The semi-IPN microgels exhibited good pH- and temperature-sensitivity, which could respond independently to both pH and temperature changes.     

Preparation of metal adsorbent from poly(methyl acrylate)-grafted-cassava starch via gamma irradiation

Metal adsorbent containing hydroxamic acid groups was successfully synthesized by radiation-induced graft copolymerization of methyl acrylate (MA) onto cassava starch. The optimum conditions for grafting were studied in terms of % degree of grafting (Dg). Conversion of the ester groups present in poly(methyl acrylate)-grafted-cassava starch copolymer into hydroxamic acid was carried out by treatment with hydroxylamine (HA) in the presence of alkaline solution. The maximum percentage conversion of the ester groups of the grafted copolymer, % Dg=191 (7.63 mmol/g of MA), into the hydroxamic groups was 70% (5.35 mmol/g of MA) at the optimum condition. The adsorbent of 191%Dg had total adsorption capacities of 2.6, 1.46, 1.36, 1.15 and 1.6 mmol/g-adsorbent for Cd²⁺, Al³⁺, UO₂²⁺, V⁵⁺ and Pb²⁺, respectively, in the batch mode adsorption.     

Proton-conducting membranes based on poly(2,5-benzimidazole) (ABPBI) and phosphoric acid prepared by direct acid casting

We report the preparation of phosphoric acid doped poly(2,5-benzimidazole) (ABPBI) membranes for PEMFC by simultaneously doping and casting from a poly(2,5-benzimidazole)/phosphoric acid/methanesulfonic acid (MSA) solution. The evaporation of MSA yields a very homogeneous membrane having a better controlled composition, avoiding the use of solvent-intensive procedures. Membranes have been prepared with contents of up to 3.0H₃PO₄ molecules per ABPBI repeating unit. These membranes achieve a maximum conductivity of 1.5 × 10⁻² S cm⁻¹ at temperatures as high as 180 °C in dry conditions. These ABPBI membranes are more conveniently prepared than those conventionally formed and doped in separate steps while featuring comparable conductivities (ABPBI × 2.7H₃PO₄ prepared by the soaking method showed a conductivity of 2.5 × 10⁻² S cm⁻¹ at 180 °C in dry conditions).     

Pervaporation separation of aromatic/aliphatic hydrocarbons by crosslinked poly(methyl acrylate-co-acrylic acid) membranes

Copolymers of methyl acrylate and acrylic acid were synthesized to fabricate membranes ionically crosslinked using aluminum acetylacetonate for the separation of toluene/i-octane mixtures by pervaporation at high temperatures. The formation of the ionic crosslinking via bare aluminum cations was characterized by UV–VIS spectroscopy and solubility tests. Reproducibility and the reliability of the methodology for membrane formation and crosslinking were confirmed. The effects of acrylic acid content, crosslinking conditions, pervaporation temperature, and feed composition on the normalized flux and the selectivity for toluene/i-octane mixtures were determined. A typical crosslinked membrane showed a normalized flux of 26 kg μm m⁻² h⁻¹ and a selectivity of 13 for a 50/50 wt.% feed mixture at 100°C. The pervaporation properties including solubility selectivity and diffusivity selectivity are discussed in terms of swelling behavior. The performance of the current membranes were benchmarked against other membrane materials reported in the literature.     

Post-irradiation time effects on the graft of poly(ethylene-alt-tetrafluoroethylene) (ETFE) films for ion exchange membrane application

Grafting of styrene followed by sulfonation onto poly(ethylene-alt-tetrafluoroethylene) (ETFE) was studied for synthesis of ion exchange membranes. Radiation-induced grafting of styrene onto ETFE films was investigated after simultaneous irradiation (in post-irradiation condition) using a ⁶⁰Co source. The ETFE films were irradiated at 20 kGy dose at room temperature and chemical changes were monitored after contact with styrene for grafting. The post-irradiation time was established at 14 days when the films were remained in styrene/toluene 1:1 v/v. After this period the grafting degree was evaluated in the samples. The grafted films were sulfonated using chlorosulfonic acid and 1, 2-dichloroethane 20:80 (v/v) at room temperature for 5 h. The membranes were analyzed by infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), thermogravimetric measurements (TG) and degree of grafting (DOG). The ion exchange capacity (IEC) of membranes was determined by acid–base titration and the values for ETFE membranes were achieved higher than Nafion^® films. Preliminary single cell performance was made using pure H₂ and O₂ as reactants at a cell temperature of 80 °C and atmospheric gas pressure. The fuel cell performance of ETFE films was satisfactory when compared to state-of-art Nafion^® membranes.     

Structure and swelling-release behaviour of poly(vinyl pyrrolidone) (PVP) and acrylic acid (AAc) copolymer hydrogels prepared by gamma irradiation

Copolymer network hydrogels were prepared by gamma irradiation of aqueous solutions of poly(vinyl pyrrolidone) (PVP) and acrylic acid monomer (AAc). The composition of the final hydrogels compared to the composition of the initial preparation solutions of hydrogels was determined. The chemical structure and nature of bonding was characterized by IR spectroscopy analysis, while the thermal durability of the prepared hydrogels was assessed by thermogravimetric analysis (TGA). The kinetic swelling in water and the pH-sensitivity of PVP/AAc copolymer hydrogels was studied. The drug release properties of PVP/AAc hydrogels taking methyl orange indicator as a drug model was investigated. The IR spectra indicate the formation of copolymer networks, whereas the TGA study showed that the PVP/AAc hydrogels possess higher thermal stability than pure PAAc and lower than PVP hydrogels. The kinetic swelling in water showed that all the hydrogels reached equilibrium after 24 h and that the degree of swelling increases with increasing the ratio of AAc in the initial feeding solutions. It was found that the degree of swelling of PVP/AAc hydrogels increases greatly within the pH range 4-7 depending on composition.     

Removal of cationic dyes by poly(acrylamide-co-acrylic acid) hydrogels in aqueous solutions

Poly(acrylamide-co-acrylic acid (poly(AAm-co-AAc)) hydrogels prepared by irradiating with γ-radiation were used in experiments on swelling, diffusion, and uptake of some cationic dyes such as Safranine-O (SO) and Magenta (M). Poly(AAm-co-AAc) hydrogels irradiated at 8.0 kGy have been used for swelling and diffusion studies in water and cationic dye solutions. The maximum swellings in water, and SO, and M solutions observed are 2700%, 3500%, and 4000%, respectively. Diffusions of water and cationic dyes within hydrogels have been found to be non-Fickian in character. Adsorption of the cationic dyes onto poly(AAm-co-AAc) hydrogels is studied by the batch adsorption technique. The adsorption type was found Langmuir type in the Giles classification system. The moles of adsorbed dye for SO and M per repeating unit in hydrogel (binding ratio, r) have been calculated as 3834×10⁻⁶ and 1323×10⁻⁶, respectively. These results show that poly(AAm-co-AAc) hydrogels can be used as adsorbent for water pollutants such as cationic dyes.     

疏水化修饰的聚N-异丙基丙烯酰胺高分子的水溶液性质研究

为了研究不同疏水化修饰的聚Ｎ 异丙基丙烯酰胺（ＰＮＩＰＡＭ）高分子的水溶液性质,合成了一系列Ｎ 异丙基丙烯酰胺（ＮＩＰＡＭ）和长链丙烯酸酯及丙烯酸胆固醇酯的共聚物．利用表面张力法证实了该类共聚物在室温下都具有良好的表面活性,在水溶液中能够形成胶束．利用荧光探针法,研究了共聚物的低温临界溶液温度（ＬｏｗｅｒＣｒｉｔｉｃａｌＳｏｌｕｔｉｏｎＴｅｍｐｅｒａｔｕｒｅ,ＬＣＳＴ）,发现,随着丙烯酸酯碳链及其配比（摩尔投料比）的变化,共聚物的ＬＣＳＴ变化不明显,但它们都比均聚的ＰＮＩＰＡＭ要低;利用荧光偏振法研究了共聚物在水溶液中的微粘度,发现其微粘度不随共聚物中丙烯酸酯链长和配比的变化而变化,说明了该类共聚物在室温下能够形成相类同的胶束内核．     

A novel process to prepare porous membranes comprising SnO2 nanoparticles and P(MMA-AN) as polymer electrolyte

We have successfully developed a new process to prepare porous poly(methyl methacrylate-co-acrylonitrile) (P(MMA-AN)) copolymer based gel electrolyte. The porous structure in the polymer matrix is achieved by adding SnO₂ nanoparticles which are mostly used as gas sensor materials. The quasi-aromatic solvent, NMP, has an electron-repulsion effect with the space charge layer on the surface of SnO₂ nanoparticles and forms a special gas–liquid phase interface. Once the cast polymer solution is stored at an elevated temperature to evaporate the solvent, gas–liquid phase separation happens and spherical pores are obtained. The ionic conductivity at room temperature of the prepared gel polymer electrolyte based on the porous membrane is as high as 1.54 × 10⁻³ S cm⁻¹ with the electrochemical stability up to 5.10 V (vs. Li/Li⁺). This method presents another promising way to prepare porous polymer electrolyte for practical use.     

Novel amphiphilic triblock copolymer based on PPDO,PCL, and PEG: Synthesis,characterization, and aqueous dispersion

Amphiphilic triblock copolymer, poly(p-dioxanone-co-caprolactone)-block-poly(ethylene oxide)-block-poly(p-dioxanone-co-caprolactone) (PPDO-co-PCL-b-PEO-b-PPDO-co-PCL) was synthesized by ring opening polymerization (ROP) of p-dioxanone and ɛ-caprolactone initiated through the hydroxyl end of poly(ethylene glycol) (PEG) in the presence of stannous 2-ethyl hexanoate [Sn(oct)₂] as a catalyst. Polymerization and structural features of the polymers were analyzed by different physicochemical techniques (GPC, ¹H NMR, ¹³C NMR, FT-IR, DSC and TGA). The splitting of ¹H NMR resonance at δ 2.3 and δ 4.1 ppm reveals the random copolymerization. Polymeric nanoparticles were prepared in phosphate buffer (pH 7.4) by co-solvent evaporation technique at room temperature (25 °C). Existence of hydrophobic domains as cores of the micelles were characterized by ¹H NMR spectroscopy and further confirmed with fluorescence technique using pyrene as a probe. Critical micelle concentration (CMC) of the polymer in phosphate buffer (pH. 7.4) was decreased from 2.3 × 10⁻³ to 7.6 × 10⁻⁴ g/L with the fraction of PCL. Polymeric nanoparticles observed by atomic force microscopy (AFM) were uniform and spherical, with smooth textured of around 50–30 nm diameter. Dynamic light scattering (DLS) and electrophoretic light scattering (ELS) measurements showed a monodisperse size distribution of around 113–90 nm hydrodynamic diameters and negative zeta (ζ) potential (−4 to −14 mV), respectively. The investigations for the polymeric nanoparticles in aqueous medium showed that the composition of the hydrophobic segment of amphiphilic block copolymer makes a significant influence on its physicochemical characteristics.