Incorporation Of Acrylic Acid Research Articles

Crosslinking and Swelling Properties of pH-Responsive Poly(Ethylene Glycol)/Poly(Acrylic Acid) Interpenetrating Polymer Network Hydrogels.

This study investigates the crosslinking dynamics and swelling properties of pH-responsive poly(ethylene glycol) (PEG)/poly(acrylic acid) (PAA) interpenetrating polymer network (IPN) hydrogels. These hydrogels feature denser crosslinked networks compared to PEG single network (SN) hydrogels. Fabrication involved a two-step UV curing process: First, forming PEG-SN hydrogels using poly(ethylene glycol) diacrylate (PEGDA) through UV-induced free radical polymerization and crosslinking reactions, then immersing them in PAA solutions with two different molar ratios of acrylic acid (AA) monomer and poly(ethylene glycol) dimethacrylate (PEGDMA) crosslinker. A subsequent UV curing step created PAA networks within the pre-fabricated PEG hydrogels. The incorporation of AA with ionizable functional groups imparted pH sensitivity to the hydrogels, allowing the swelling ratio to respond to environmental pH changes. Rheological analysis showed that PEG/PAA IPN hydrogels had a higher storage modulus (G') than PEG-SN hydrogels, with PEG/PAA-IPN5 exhibiting the highest modulus. Thermal analysis via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) indicated increased thermal stability for PEG/PAA-IPN5 compared to PEG/PAA-IPN1, due to higher crosslinking density from increased PEGDMA content. Consistent with the storage modulus trend, PEG/PAA-IPN hydrogels demonstrated superior mechanical properties compared to PEG-SN hydrogels. The tighter network structure led to reduced water uptake and a higher gel modulus in swollen IPN hydrogels, attributed to the increased density of active network strands. Below the pKa (4.3) of acrylic acid, hydrogen bonds between PEG and PAA chains caused the IPN hydrogels to contract. Above the pKa, ionization of PAA chains induced electrostatic repulsion and osmotic forces, increasing water absorption. Adjusting the crosslinking density of the PAA network enabled fine-tuning of the IPN hydrogels' properties, allowing comprehensive comparison of single network and IPN characteristics.

Pengaruh Iradiasi Gamma dan Asam Akrilat terhadap Sifat Mekanik Polimer Super Water Absorbent (SWA) Berbasis Onggok

The Super Water Absorbent (SWA) polymer is a type of polymer that has exceptional water absorption capabilities while remaining insoluble in water. In this study, the authors conducted research on the modification of SWA by including acrylic acid and acrylamide monomers, followed by a crosslinking process utilising gamma irradiation. This study investigated the impact of acrylic acid and gamma irradiation on the mechanical characteristics of SWA. The experimental findings demonstrated a notable enhancement in the mechanical properties of the hydrogel by the incorporation of acrylic acid. This was evidenced by a substantial rise in the hardness value, which rose from 11.09 mJ to 36.13 mJ.

Synthesis and characterization of chitosan-based graft copolymers with temperature-switchable and self-adaptive plugging performance for drilling in microporous formation

The increasing oil–gas explorations in microporous formations and the intensified environmental requirements necessitate the development of high-performance, environmentally friendly and sustainable plugging materials to maintain wellbore stability in drilling engineering. In this work, a series of graft copolymers of carboxymethyl chitosan-g-poly(oligo(ethylene glycol) methyl ether methacrylate-co-acrylic acid) (GCOA) is synthesized through free-radical graft-from polymerization. The oligo(ethylene glycol) methyl ether methacrylate (OEGMA) and acrylic acid (AA) can be well copolymerized in the grafts as confirmed by structural characterizations, and the incorporation of AA improves the grafting ratio and grafting efficiency. All obtained GCOAs possess the temperature-responsive aggregation behavior, which causes the formation of aggregated meso-assemblies from original nano-micelles when heating above their lower critical solution temperature (LCST), accompanied by the phase separation. Meanwhile, the presence of AA segments increases the LCST due to the resistance of enhanced polymer–polymer electrostatic repulsion to the hydrophobic attraction. By the delicate control of AA molar ratio from 0 to 50 mol%, the LCST values of GCOAs can be adjusted from 90 °C to 110 °C. Furthermore, the GCOAs are formulated as smart plugging fluids and the intelligent plugging evaluation method is established based on core flow test with continuous temperature control. The results indicate that the GCOAs can form effective plugging in both low- and median-permeability cores when temperature reaches above a switching point and the formed plugging can be partially removed after cooling, showing the temperature-switchable and self-adaptive plugging capacity as a consequence of reversible retention of GCOA aggregates and thermo-thickening behavior in pore-throat spaces. These features enable the implementation and removal of in-situ plugging in the specific temperature sections during drilling, and provide a new insight into the design of novel smart plugging materials with sustainable and recycling values.

Preparation and characterization of self-crosslinking fluorinated polyacrylate latexes and their pressure sensitive adhesive applications

Self-crosslinking fluorinated polyacrylate latexes based on butyl acrylate (BA), fluorine monomer octafluoropentyl methacrylate (OFPMA), self-crosslinking functional monomers acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA) were synthesized by a monomer-starved seeded semi-continuous emulsion polymerization process. The latexes and their corresponding films were characterized by laser particle size analyser, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), contact angle goniometer, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Results indicated that the particle size of the latexes and the gel content of the films were both independent of the amount of OFPMA employed. On the other hand, the particle size of the latexes decreased and the gel content of the films increased with the incorporation of AA and HEA as expected. Glass transition temperature (Tg) and the thermal stability of the copolymer were both improved gradually as OFPMA content increased. XPS, AFM and water contact angle measurement indicated that the fluoroalkyl groups had a tendency to enrich on the surface of the films. However, this enrichment of fluorine on the film surface was reduced after the introduction of self-crosslinking functional monomers into the system. Finally, the adhesive property of the latexes was evaluated for application as a pressure sensitive adhesive (PSA).

Hexavalent chromium removal by polyacrylic acid-grafted Macadamia nutshell powder through adsorption–reduction mechanism: Adsorption isotherms, kinetics and thermodynamics

Hydrochloric acid-treated Macadamia nutshell (AMM) powder was grafted with acrylic acid monomers at different doses of 0.5, 1.0 and 2.0 M to incorporate the carboxylic groups on its surface. The grafted materials were labeled 0.5 GAM, 1 GAM and 2 GAM signifying the grafting ratios. The incorporation of acrylic acid was demonstrated by an increase in oxygen content from 0.18% to 1.20% in the elemental analysis. The splitting and shifting of the alcohol intermolecular bonded –OH functional groups at 3330 cm−1 to 3396 and 3321 cm−1 observed after grafting was further proof of the addition of acrylic acid. Scanning electron microscopy (SEM) images revealed that the materials exhibited stacked sheets with spherical halo openings typical of biomaterials. The maximum conditions for chromium(VI) removal were obtained at pH 2, 180 min contact time, 7.5 g/L adsorbent dosage concentration and a temperature of 40 °C. The adsorption mechanism was best described by the monolayer sorption postulated by Langmuir with reported adsorption capacity of 39.21 mg/g. The best fit for the kinetic data was obtained with the pseudo-second-order rate model suggesting a chemisorption nature of interaction. Accordingly, the thermodynamic factors were feasible, spontaneous and endothermic. The acrylic acid-functionalized Macadamia adsorbent showed greater potential compared to other biosorbents in the removal of hexavalent chromium from aqueous solution in the presence of competing anions.

Improvement in the blood compatibility of polyvinylidene fluoride membranes via in situ cross‐linking polymerization

In this study, we have provided a highly efficient, convenient, and universal protocol for preparing polyvinylidene fluoride (PVDF) membranes with low blood contact activation via in situ cross‐linking copolymerization of 2‐hydroxyethl methacrylate (HEMA) and acrylic acid (AA) in a solution of PVDF. The modified membranes were prepared from PVDF solution by phase inversion technology. The composition and morphology of the modified membranes were confirmed by attenuated total reflectance‐Fourier transform infrared (ATR‐FTIR) spectroscopy, thermogravimetric (TG) analysis, and scanning electron microscopy (SEM). Protein adsorption, clotting time, and contact activation on the modified PVDF membranes were systematically studied, the results indicating that after the incorporation of AA and HEMA, the modified PVDF membranes possessed anticoagulant properties in addition to low contact activation of blood components when in contact with blood. Therefore, fluorinated PVDF membranes with surfaces enriched with carboxyl and hydroxyl groups possessed the potential for use in long‐term blood‐contacting devices.

Smart pH-Responsive Antimicrobial Hydrogel Scaffolds Prepared by Additive Manufacturing.

We report on the fabrication of 3D printed pH-responsive and antimicrobial hydrogels with a micrometer-scale resolution achieved by stereolithography (SLA) 3D printing. The preparation of the hydrogels was optimized by selecting the most appropriate difunctional polyethylene glycol dimethacrylates (testing cross-linking agents with chain lengths ranging from 2 up to 14 units ethylene glycol) and introducing acrylic acid (AA) as a monofunctional monomer. As a result of the incorporation of AA, the hydrogels described are able to reversibly swell and shrink upon environmental changes on the pH, and the swelling extent is directly related to the amount of AA and can be thus finely tuned. More interestingly, upon optimization of the UV penetration depth employing a photoabsorber (Sudan I), a reliable procedure for the fabrication of 3D objects with a high model accuracy is shown. Finally, the antimicrobial properties of all of the hydrogels were demonstrated using Staphylococcus aureus as a bacterial model. We found that even those hydrogels with a low amount of AA monomeric units presented excellent antimicrobial properties against S. aureus.

Poly(AA-co-VPA) hydrogel cross-linked with N-maleyl chitosan as dye adsorbent: Isotherms, kinetics and thermodynamic investigation

In this study, hydrogel polymer was synthesized by incorporation of acrylic acid (AA), vinylphosphonic acid (VPA) and N-maleyl chitosan which was prepared through the acylation reaction between maleic anhydride and chitosan. N-maleyl chitosan crosslinked P(AA-co-VPA) hydrogel was utilized for the effective adsorption of crystal violet (CV) and methylene blue (MB) dyes from aqueous solutions. The synthesized hydrogel was characterized by using FTIR, SEM, EDS, TGA-DTA, and DSC methods. The effecting parameters on adsorption of dyes such as initial concentration of dyes, temperature, pH and adsorbent polymer dose were studied. The adsorption isotherm was analyzed in different temperature using Langmuir, Freundlich, Temkin and Redlich-Peterson models and the adsorption data were well described by Redlich-Peterson isotherm model. The adsorption kinetics was analyzed using pseudo first-order, pseudo second-order, intraparticle and film diffusion models in 20, 30, 40 and 50 mg/L of dye solutions and the adsorption data were well described by pseudo-second-order model. The maximum adsorption capacity of the hydrogel polymer for removal of CV and MB in 50 mg/L of dye solutions was 64.56 mg/g and 66.89 mg/g, respectively. Thermodynamic studies recommended that the adsorption process was endothermic and spontaneous. Furthermore, the adsorbent was successfully employed for successive four cycles of adsorption-desorption.

Preparation of Linear Low-Density Polyethylene-g-Poly(Acrylic Acid)-Co-Starch Hydrogel

In this work, a type of hydrogel from waste linear low density polyethylene (LLDPE), acrylic acid (AA), and starch was prepared using N, N-methylenebisacrylamide (MBA) as the crosslinker, and benzoyl peroxide as the initiator. The hydrogel was characterized by Fourier transform infrared spectroscope (FTIR), scanning electron micrograph (SEM), and X-ray diffraction (XRD). The results confirmed the incorporation of acrylic acid and starch in the LLDPE chain. SEM results show that the prepared hydrogel has a porous structure. Product showed maximum water absorbency of 180 g/g in distilled water.

Preparation and characterization of microencapsulated n-octadecane as phase change material with different n-butyl methacrylate-based copolymer shells

Microcapsules containing n-octadecane with different n-butyl methacrylate (BMA)-based copolymer shells were fabricated by a suspension-like polymerization method. n-butyl acrylate (BA), methacrylic acid (MAA) and acrylic acid (AA) were employed as monomers to copolymerize with BMA. The surface morphologies of the microencapsulated phase change materials (MicroPCMs) were studied by scanning electron microscopy (SEM). The thermal properties, thermal reliabilities and thermal stabilities of the MicroPCMs were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The temperature-regulated properties of the MicroPCMs were determined by an infrared thermography. The incorporation of MAA or AA to the acrylic composition of the polymer shells led to an increase in both the heat storage capacities and thermal stabilities of the MicroPCMs. The MicroPCMs with P(BMA-co-MAA) exhibit a greater heat capacity and thermal stability compared with the MicroPCMs with P(BMA-co-AA). The MicroPCMs with P(BMA-co-MAA) have the highest latent heats of melting (144.3J/g) and crystallization (152.9J/g) as well as the highest thermal resistant temperature (249°C). The phase change temperatures and enthalpies of the MicroPCMs varied little after 1000 thermal cycles. Thermal images showed that the gypsum board containing the MicroPCMs with BMA-based copolymers as shells, especially with P(BMA-co-MAA) and P(BMA-co-AA) as shells, possessed temperature-regulated properties. As a result, the MicroPCMs with BMA-based copolymers as shells have good thermal energy storage and thermal regulation potentials, such as solar energy-saving building materials.

Temperature- and pH-sensitive nanohydrogels of poly(N-Isopropylacrylamide) for food packaging applications: modelling the swelling-collapse behaviour.

Temperature-sensitive poly(N-isopropylacrylamide) (PNIPA) nanohydrogels were synthesized by nanoemulsion polymerization in water-in-oil systems. Several cross-linking degrees and the incorporation of acrylic acid as comonomer at different concentrations were tested to produce nanohydrogels with a wide range of properties. The physicochemical properties of PNIPA nanohydrogels, and their relationship with the swelling-collapse behaviour, were studied to evaluate the suitability of PNIPA nanoparticles as smart delivery systems (for active packaging). The swelling-collapse transition was analyzed by the change in the optical properties of PNIPA nanohydrogels using ultraviolet-visible spectroscopy. The thermodynamic parameters associated with the nanohydrogels collapse were calculated using a mathematical approach based on the van't Hoff analysis, assuming a two-state equilibrium (swollen to collapsed). A mathematical model is proposed to predict both the thermally induced collapse, and the collapse induced by the simultaneous action of two factors (temperature and pH, or temperature and organic solvent concentration). Finally, van't Hoff analysis was compared with differential scanning calorimetry. The results obtained allow us to solve the problem of determining the molecular weight of the structural repeating unit in cross-linked NIPA polymers, which, as we show, can be estimated from the ratio of the molar heat capacity (obtained from the van't Hoff analysis) to the specific heat capacity (obtained from calorimetric measurements).

Selective removal of 90Sr and 60Co from aqueous solution using N-aza-crown ether functional poly(NIPAM) hydrogels

The ability of temperature and pH responsive cross-linked poly(NIPAM-co-AAc) hydrogel beads containing covalently bound N-aza-crown ethers to selectively complex 90Sr and 60Co under competitive and non-competitive conditions is demonstrated using a combination of autoradiography and scintillation measurements. Due to the presence of copolymerised acrylic acid, which is incorporated to introduce pH responsive behaviour as well as acting as the site of covalent attachment of the N-aza-crown ether, the decrease in particle diameter as a function of increasing temperature on going through the LCST of PNIPAM is reduced in the presence of electrolyte. At pH 2 no complexation of either 90Sr or 60Co was observed. At pH 7 the incorporation of acrylic acid under non-competitive conditions results in the ability to complex ca. 90% 90Sr and 60Co which increases to between 94% and 96% on inclusion of N-aza-crown ether. Under competitive conditions the hydrogels lose the ability to selectively complex 90Sr, although the selectivity for 60Co was enhanced in the presence of N-aza-crown ether. Subsequent recovery of bound 60Co from the hydrogel on lowering to pH 2 was only partially successful, and lead to a decrease in the swelling behaviour on readjustment to pH 7.

Synthesis of novel poly(N,N-diethylacrylamide-co-acrylic acid) (P(DEA-co-AA)) microgels as carrier of horseradish peroxidase immobilization for pollution treatment

A series of temperature-sensitive N,N-diethylacrylamide-co-acrylic acid microgels were synthesized by modified surfactant-free emulsion polymerization method and characterized by Fourier transform infrared spectroscopy, turbidimetric method, scanning electron microscopy (SEM), and dynamic light scattering (DLS) measurements. The SEM images showed that the as-synthesized microgels were monodispersed as spherical particles and the average size increased from 200 to 800 nm with the mole fraction of acrylic acid (AA) increasing from 0 to 0.40. Turbidimetric analysis and DLS investigation indicated that the volume phase transition temperature and the swelling ratio of the microgels had an upward trend that was associated with the higher incorporation of AA. Furthermore, horseradish peroxidase (HRP) was successfully immobilized on the microgel with the greatest swelling ratio (the mole fraction of AA equal to 0.40) to obtain an enzyme-microgel complex for the treatment of wastewater polluted by phenolic compounds. The immobilized HRP achieved a high removal efficiency of >96% toward phenol and was more thermostable and more easily stored and reused compared with free HRP.

금속코팅용 광경화 코팅필름의 물성에 대한 아크릴산(Acrylic acid)의 영향

본 연구에서는 스테인레스 스틸(stainless steel)의 표면 코팅용 광경화 필름 개발을 위하여 isophorone diisocyanate (IPDI), polycaprolactone triol(PCLT), 2-hydroxyethyl acrylate(HEA), 그리고, 희석제로서 trimethylolpropane triacrylate (TMPTA)와 acrylic acid(AA)의 첨가비율을 달리한 광경화형 poly(urethane acrylate-co-acrylic acid)(PU-co-AA) 필름을 성공적으로 제조하였으며, 제조한 PU-co-AA 필름의 모폴로지, 접착특성, 기계적 특성, 전기적 특성 등에 대한 AA 첨가량의 영향을 조사하였다. 모든 PU-co-AA 필름은 비정형 구조를 나타내었으나, AA의 함량이 증가할수록 분자 규칙 및 패킹밀도는 감소하였다. 접착특성은 AA 함량 50% 이상에서는 접착력 5B 수준으로 스테인레스 스틸에 대한 우수한 접착특성을 나타내었으며, AA 함유량이 0%에서 66%까지 증가함에 따라 Pull-off strength법 접착력은 6~31 <TEX>$kg_f/cm^2$</TEX> 로 선형적으로 증가하였다. 광경화 폴리우레탄 아크릴레이트의 접착력을 증가시키기 위한 유연한 사슬구조와 2관능기를 가진 AA의 도입은 다관능기의 TMPTA의 높은 가교밀도를 줄임으로써 효과적인 것을 확인할 수 있었으며, AA 함량이 증가함에 따라 접촉각의 감소와 젖음성의 향상을 확인하였다. 한편, 유연한 사슬 및 곁사슬 -COOH를 가진 AA의 도입은 규칙성 및 패킹밀도의 감소를 나타내며, 이는 PU-co-AA 필름의 경도 저하를 나타내며, 또한 AA의 분자 내의 작용기 -COOH는 고분자 필름 내의 분극현상을 증가시킴으로써 유전상수의 증가 경향을 나타내었다. 결론적으로 PU-co-AA 필름의 물리적 특성은 첨가한 AA의 함량에 크게 의존함을 확인할 수 있었다. 또한, 광경화 폴리우레탄 아크릴레이트에 아크릴산 AA의 도입은 사슬의 유연성 증가와 가교밀도의 감소 영향으로 스테인레스 스틸과의 접착력을 향상시키는데 매우 효과적인 방법임을 확인할 수 있었다. Five different composition UV-cured poly(urethane acrylate-co-acrylic acid) (PU-co-AA) films have been prepared by reacting isophorone diisocyanate(IPDI), polycaprolactone triol(PCLT), 2-hydroxyethyl acrylate(HEA), and different weight ratio trimethylolpropane triacrylate(TMPTA) and acrylic acid(AA) as diluents, and characterized using a Fourier transform infrared spectroscopy(FT-IR). The adhesion properties onto the stainless steel, morphology, mechanical hardness, and electrical property of UV-cured PU-co-AA films were investigated as a function of acrylic acid(AA) content. All the PU-co-AA films are structure-less and the molecular ordering and packing density decreased with increasing content of AA due to the flexible structure and -COOH side chains in AA. The crosscut test showed that PU-co-AA films without AA and with low content of AA showed 0% adhesion(0B) and the adhesion of PU-co-AA films in the range of 40-50% AA increased dramatically as the content of AA increases. The pull-off measurements showed that the adhesion force of PU-co-AA films to stainless steel substrate varied from 6 to 31 kgf /<TEX>$cm^2$</TEX> and increased linearly with increasing AA content. The mechanical hardness also decreased as the content of AA increases. This may come from relatively linear and flexible structure in AA and low crystallinity in PU-co-AA films with higher content of AA. The higher AA-containing PU-co-AA films showed higher dielectric constant due to the increase of polarization by introducing AA monomer. In conclusion, the physical properties of UV-cured PU-co-AA films are strongly dependent upon the content of AA and the incorporation of AA in polyurethane acrylate is very useful way to increase the adhesion strength of UV-curable polymers on the stainless steel substrate.

Self-association properties of HPMA copolymers containing an amphipathic heptapeptide

Receptor-binding peptides are suitable targeting moieties for macromolecular therapeutics. Binding several targeting peptides to one macromolecule may improve biorecognition due to the multivalency effect. On the other hand, the resulting amphipathic structure of such conjugates may result in the association of side-chains with a concomitant decrease in the accessibility of the side-chain-bound ligands. Using the one-bead one-compound combinatorial method, we have recently identified a heptapeptide (YILIHRN; HP) ligand for the CD21 receptor (Biomacromolecules 7, 3037, 2006). Here, we evaluated the relationship between structure and self-association of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-HP conjugates using fluorescence resonance energy transfer (FRET) to evaluate their conformation in solution. In addition to HP, HPMA copolymers containing side-chains terminating in tryptophan (energy donor) and dansyl (energy acceptor) were synthesized, and solutions were evaluated using an excitation wavelength of 295 nm (ratio of emission intensity 510 nm/370 nm indicated energy transfer efficiency). It was found that higher HP content correlated with higher FRET efficiency, indicating the formation of compact coils. Modification of the HPMA copolymer backbone by the incorporation of acrylic acid (AA) comonomer units resulted in decreased FRET efficiency, presumably due to the expansion of the polymer coils as a result of electrostatic repulsion. The dependence of FRET efficiency on pH was in agreement with the ionization profile of the AA residues.To determine the effect of HP content on enzymatic drug release kinetics, HPMA copolymer-HP conjugates containing GFLG side-chains terminating with doxorubicin (DOX) were incubated with papain and the release of free DOX monitored. When HP content increased above a particular threshold, the rate of DOX release decreased as a result of self-association of HPMA copolymer-GFLG-DOX-HP conjugates. The FRET data correlated well with hydrodynamic volumes determined by size exclusion chromatography (SEC), with molecular weights determined by light scattering, and with the kinetics of drug release.

Effect of microstructure of acrylic copolymer/terpolymer on the properties of silica based nanocomposites prepared by sol–gel technique

Acrylic copolymers/terpolymers with different comonomer contents were prepared by solution polymerization. Copolymers/terpolymers-silica hybrid composites were synthesized by acid catalyzed sol–gel technique using tetraethoxysilane (TEOS) as silica precursor. Microstructure of the copolymers and the terpolymers was analyzed by C13 nuclear magnetic resonance and Fourier transform infrared (FTIR) spectroscopy. The hybrid composites were characterized by scanning electron microscopy (SEM), FTIR, thermogravimetry, dynamic mechanical thermal analysis (DMTA) and their mechanical properties. The results showed that an increase in hydrophilicity of the polymer matrix and the ratio of ethyl to butyl acrylate, and incorporation of acrylic acid as termonomer helped in finer dispersion of silica and prevented macrophase separation. There was no evidence of chemical interaction between the polymer and the dispersed silica phase. Dynamic mechanical thermal analysis indicated mechanical reinforcement within the hybrid composites. As a result, these composites demonstrated superior tensile strength and tensile modulus with increasing proportion of TEOS up to a certain level. At a particular TEOS concentration, the tensile properties improved with increasing hydrophilicity of the polymer matrix and acrylic acid modification. The mechanism for improvement in mechanical and dynamic mechanical properties of the hybrids was discussed.

Physical and mechanical properties of nano-CaCO3/PP composites modified with acrylic acid

Nano-CaCO3/polypropylene (PP) composites modified by the reactive monomer acrylic acid (AA) with or without the initiator dicumyl peroxide (DCP) were prepared using a two-step method. The effects of nano-CaCO3 and AA on the physical and mechanical properties of nano-CaCO3/PP composites were investigated. Differential scanning calorimetry (DSC) results showed that the incorporation of nano-CaCO3 increased the crystallisation temperature as a result of the heterogeneous nucleation effect of nano-CaCO3 on PP, and induced the formation of β phase PP. The addition of AA further increased the crystallisation temperature of PP and the intensity of β phase PP. The mechanical tests indicated that nano-CaCO3 could simultaneously reinforce and toughen PP, and the mechanical properties of nano-CaCO3/PP composites were higher than those of micro-CaCO3/PP composites. In addition, incorporation of AA further increased the mechanical properties of the composites. In the presence of DCP, a small amount of AA could increase markedly the mechanical properties of nano-CaCO3/PP composites.

Mechanical properties of Mg(OH)2/polypropylene composites modified by functionalized polypropylene

AbstractModified Mg(OH)2/polypropylene (PP) composites were prepared by the addition of functionalized polypropylene (FPP); and acrylic acid (AA) and by the formation of in situ FPP. The effects of the addition of FPP and AA and the formation of in situ FPP on the mechanical properties of Mg(OH)2/PP composites were investigated. Experimental results indicated that the addition of Mg(OH)2 markedly reduced the mechanical properties of PP. The extent of reduction in notch impact strength of PP was higher than that in flexural strength and tensile strength. However, tensile modulus and flexural modulus increased with increased Mg(OH)2 content. The addition of FPP facilitated the improvement in the flexural strength and tensile strength of Mg(OH)2/PP composites. The higher the Mg(OH)2 content was, the more significant the effect of FPP was. The incorporation of AA resulted in further increased mechanical properties, in particular the flexural strength, tensile strength, and notch impact strength of Mg(OH)2/PP composites containing high levels of Mg(OH)2. It not only improved mechanical properties but also increased the flame retardance of Mg(OH)2/PP composites. Although the mechanical properties of composites modified by the formation of in situ FPP were lower than those of composites modified by only the addition of AA in the absence of diamylperoxide, the mechanical properties did not decline with increased Mg(OH)2 content. Moreover, the mechanical properties increased with increasing AA content. The addition of an oxidation resistant did not influence the mechanical properties of the modified Mg(OH)2/PP composites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2139–2147, 2003

The incorporation of carboxylate groups into temperature-responsive poly(N-isopropylacrylamide)-based hydrogels promotes rapid gel shrinking

Aqueous gel deswelling rates for copolymer hydrogels comprising N-isopropylacrylamide (IPAAm) and 2-carboxyisopropylacrylamide (CIPAAm) in response to increasing temperatures were investigated. Compared with pure IPAAm-based gels, IPAAm–CIPAAm gels shrink very rapidly in response to small temperature increases across their lower critical solution temperature (their volume is reduced by five-sixths within 60 s). Shrinking rates for these hydrogels increase with increasing CIPAAm content. In contrast, structurally analogous IPAAm–acrylic acid (AAc) copolymer gels lose their temperature sensitivity with the introduction of only a few mole percent of AAc. Additionally, deswelling rates of IPAAm–AAc gels decrease with increasing AAc content. These results indicate that IPAAm–CIPAAm copolymer gels behave distinctly from IPAAm–AAc systems even if both comonomers, CIPAAm and AAc, possess carboxylic acid groups. Thus, we propose that the sensitive deswelling behavior for IPAAm–CIPAAm gels results from strong hydrophobic chain aggregation maintained between network polymer chains due to the similar chemical structures of CIPAAm and IPAAm. This structural homology facilitates aggregation of chain isopropylamide groups for both IPAAm and CIPAAm sequences with increasing temperature. The incorporation of AAc, however, shows no structural homology to IPAAm, inhibiting chain aggregation and limiting collapse. A functionalized temperature-sensitive poly(N-isopropylacrylamide) hydrogel containing carboxylic acid groups is possible with CIPAAm, producing rapid and large volume changes in response to smaller temperature changes. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 335–342, 2001

Synthesis and characterization of acrylic acid-containing dextran hydrogels

pH-Sensitive dextran hydrogels were prepared by free radical polymerization of methacrylate derivatized dextran, acrylic acid and N-t-butylacrylamide. Incorporation of acrylic acid in hydrogels was confirmed by Fourier transform infrared spectroscopy. The pH-dependent swelling of hydrogels was strongly influenced by the acrylic acid content, conjugation degree of methacrylate moiety with dextran and modified dextran concentration. Intermolecular polymerization that occurred to a greater extent with a lower degree of conjugation of methacrylate and/or higher concentration of modified dextran effectively increased the network density of hydrogels. An increase of acrylic acid reduced the enzymatic degradability of pre-swollen hydrogels by dextranase, although the increased equilibrium swelling was observed.