Preparation and characterization of water soluble poly(acrylic acid)–hydroxypropyl cellulose composite

Purified flax waste was obtained from flax processing wastes via subjecting the latter to alkali treatment followed by peracetic acid bleaching. The so obtained purified flax wastes were chemically modified via reacting with propylene oxide in alkaline medium. The resultant hydroxypropyl cellulose (HPC) was incorporated in a polymerization medium containing acrylic acid and potassium bromate/thiourea mixture as initiation system. The polymerization reaction was monitored by determining the total conversion percent and the rheological properties of the resultant polyacrylic acid–hydroxypropyl cellulose composite [poly(AA)–HPC]. Results obtained indicate that the optimum conditions of polymerization process were: 12 mmole KBrO₃, 4 mmole thiourea and 100 g acrylic acid/100 g HPC at 50 °C for 2 h using a material to liquor ratio of 1:5.     

Synthesis and characterization of poly(dimer acid-brassylic acid) copolymer and poly(dimer acid-pentadecandioic acid) copolymer

Poly(dimer acid-brassylic acid) [P(DA-BA)] copolymers and poly(dimer acid-pentadecandioic acid) [P(DA-PA)] copolymers were prepared by melt polycondensation of the corresponding mixed anhydride prepolymers. The copolymers were characterized by Fourier transform infrared (FTIR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), wide angle x-ray powder-diffraction, and thermal gravimetric analysis (TGA). In vitro studies show that all the copolymers are degradable in phosphate buffer at 37 degrees C, and leaving an oily dimer acid residue after hydrolysis for the copolymer with high content of dimer acid. The release profiles of hydrophilic model drug, ciprofloxcin hydrochloride, from the copolymers, follow first-order release kinetics. All the preliminary results suggested that the copolymer might be potentially used as drug delivery devices.     

Utilization of hydroxypropyl cellulose and poly(acrylic acid)-hydroxypropyl cellulose composite as thickeners for textile printing

Trials were carried out to partially replace kerosene oil with hydroxypropyl cellulose (HPC), poly(acrylic acid)-hydroxypropyl cellulose composite (poly (AA)-HPC) and their mixture in pigment printing paste. Partial replacement was carried out under a variety of conditions. Variables studied include type and concentration of the aqueous thickening agent and type of pigment dyes. In addition to that, poly (AA)-HPC composite was tried to replace sodium alginate in reactive printing. The fastness properties, color strength and stiffness were measured for the reactive and pigment printed samples.     

Preparation and characterization of the graft copolymer of chitosan with poly[rosin-(2-acryloyloxy)ethyl ester]

Graft copolymerization of rosin-(2-acryloyloxy)ethyl ester (RAEE) onto chitosan (Cts) was carried out under microwave irradiation using potassium persulfate as an initiator. The structures, morphology, and thermal properties of the Cts graft copolymer (Cts-g-PRAEE) were characterized by means of FT-IR, XRD, SEM, and TG. Also, Cts and Cts-g-PRAEE copolymer were used as carriers of fenoprofen calcium (FC), and their controlled release behavior in artificial intestinal juice were studied. The results show that the rate of release of fenoprofen calcium from the carrier of Cts-g-PRAEE copolymer becomes very slower than that of Cts in artificial intestinal juice.     

Enzyme immobilization on ultrafine cellulose fibers via poly(acrylic acid) electrolyte grafts

Ultrafine cellulose fiber (diameter 200-400 nm) surfaces were grafted with polyacrylic acid (PAA) via either ceric ion initiated polymerization or methacrylation of cellulose with methacrylate chloride (MACl) and subsequent free-radical polymerization of acrylic acid. PAA grafts by ceric ion initiated polymerization increased with increasing reaction time (2-24 h), monomer (0.3-2.4 M), and initiator (1-10 mM) concentrations, and spanned a broad range from 5.5-850%. PAA grafts on the methacrylated cellulose fibers also increased with increasing molar ratios of MACl to cellulosic hydroxyl groups (MACl/OH, 2-6.4) and monomer acrylic acid (AA) to initiator potassium persulfate (KPS) ratios ([AA]/[KPS], 1.5-6), and were in a much narrower range between 12.8% and 29.4%. The adsorption of lipase (at 1 mg/ml lipase and pH 7) and the activity of adsorbed lipase (pH 8.5, 30 degrees C), in both cases decreased with increasing PAA grafts. The highest adsorption and activity of the lipase on the ceric ion initiated grafted fibers were 1.28 g/g PAA and 4.3 U/mg lipase, respectively, at the lowest grafting level of 5.5% PAA, whereas they were 0.33 g/g PAA and 7.1 U/mg lipase, respectively, at 12.8% PAA grafts on the methacrylated and grafted fibers. The properties of the grafted fibers and the absorption behavior and activity of lipase suggest that the PAA grafts are gel-like by ceric-initiated reaction and brush-like by methacrylation and polymerization. The adsorbed lipase on the ceric ion-initiated grafted surface possessed greatly improved organic solvent stability over the crude lipase. The adsorbed lipases exhibited 0.5 and 0.3 of the initial activity in the second and third assay cycles, respectively.     

Design of mucoadhesive polymeric films based on blends of poly(acrylic acid) and (hydroxypropyl)cellulose

Mixing of aqueous solutions of poly(acrylic acid) and (hydroxypropyl)cellulose results in formation of hydrogen-bonded interpolymer complexes, which precipitate and do not allow preparation of homogeneous polymeric films by casting. In the present work the effect of pH on the complexation between poly(acrylic acid) and (hydroxypropyl)cellulose in solutions and miscibility of these polymers in solid state has been studied. The pH-induced complexation-miscibility-immiscibility transitions in the polymer mixtures have been observed. The optimal conditions for preparation of homogeneous polymeric films based on blends of these polymers have been found, and the possibility of radiation cross-linking of these materials has been demonstrated. Although the gamma-radiation treatment of solid polymeric blends was found to be inefficient, successful cross-linking was achieved by addition of N,N'-methylenebis(acrylamide). The mucoadhesive potential of both soluble and cross-linked films toward porcine buccal mucosa is evaluated. Soluble films adhered to mucosal tissues undergo dissolution within 30-110 min depending on the polymer ratio in the blend. Cross-linked films are retained on the mucosal surface for 10-40 min and then detach.     

Characterisation of carboxymethyl cellulose and polyacrylamide graft copolymer

The synthesis of carboxymethyl cellulose-g-polyacrylamide was carried out by a ceric ion induced solution polymerization technique. By varying the amount of catalyst and monomer, six different grades of graft copolymers were synthesized. These graft copolymers were characterized by elemental analysis, infrared spectroscopy, rheological studies, scanning electron microscopy, thermal analysis, viscosity measurement and X-ray diffractometry. They exhibit distinguished flocculation characteristics in various suspensions and effluents. Their flocculation and viscosifying characteristics are drastically enhanced on their hydrolysis.     

Crosslinked carboxymethylchitosan-g-poly(acrylic acid) copolymer as a novel superabsorbent polymer

A novel carboxymethylchitosan-g-poly(acrylic acid) (CMCTS-g-PAA) superabsorbent polymer was prepared through graft polymerization of acrylic acid onto the chain of carboxymethylchitosan and subsequent crosslinking. It was demonstrated by FTIR spectroscopy that acrylic acid had been graft polymerized with carboxymethylchitosan. The thermal stability of the polymer was characterized by thermogravimetric analysis. By studying the swelling ratio of the polymer synthesized under different conditions, optimization conditions were found for a polymer with the highest swelling ratio. The rate of water absorption of the polymer was high, and the swelling of the polymer fitted the process of first dynamics. The swelling ratio of the polymer was pH-dependent.     

Synthesis and characterization of RGD peptide grafted poly(ethylene glycol)-b-poly(L-lactide)-b-poly(L-glutamic acid) triblock copolymer

Advances in tissue engineering require biofunctional scaffolds that can provide not only physical support for cells but also chemical and biological cues needed in forming functional tissues. To achieve this goal, a novel RGD peptide grafted poly(ethylene glycol)-b-poly(L-lactide)-b-poly(L-glutamic acid) (PEG-PLA-PGL/RGD) was synthesized in four steps (1) to prepare diblock copolymer PEG-PLA-OH and to convert its -OH end group into -NH(2) (to obtain PEG-PLA-NH(2)), (2) to prepare triblock copolymer PEG-PLA-PBGL by ring-opening polymerization of NCA (N-carboxyanhydride) derived from benzyl glutamate with diblock copolymer PEG-PLA-NH(2) as macroinitiator, (3) to remove the protective benzyl groups by catalytic hydrogenation of PEG-PLA-PBGL to obtain PEG-PLA-PGL, and (4) to react RGD (arginine-glycine-(aspartic amide)) with the carboxyl groups of the PEG-PLA-PGL. The structures of PEG-PLA-PGL/RGD and its precursors were confirmed by (1)H NMR, FT-IR, amino acid analysis, and XPS analysis. Addition of 5 wt % PEG-PLA-PGL/RGD into a PLGA matrix significantly improved the surface wettability of the blend films and the adhesion and proliferation behavior of human chondrocytes and 3T3 cells on the blend films. Therefore, the novel RGD-grafted triblock copolymer is expected to find application in cell or tissue engineering.     

Preparation of cellulose graft poly(methyl methacrylate) copolymers by atom transfer radical polymerization in an ionic liquid

Cellulose graft poly(methyl methacrylate) copolymers were prepared by atom transfer radical polymerization (ATRP) in an ionic liquid. Cellulose chloroacetate, as a macroinitiator, was first synthesized by direct acylation of cellulose with chloroacetyl chloride without any catalysts under mild conditions in an ionic liquid, 1-allyl-3-methylimidazolium chloride (BMIMCl). Then, the macroinitiator was used for the ATRP of MMA mediated by the CuBr and 2,2′-bipyridine (bpy) catalysis system. The copolymerization was carried out in BMIMCl without homopolymer byproduct. The polymers were easily separated from the catalyst when the ionic liquid was used as reaction medium. The grafting copolymers were characterized by means of ¹H NMR, AFM and GPC. The results showed that the obtained copolymers had grafted polymer chains with well-controlled molecular weight and polydispersity, and the polymerization was a “living/controlled” system. Further, through AFM observation, it was found that the cellulose graft copolymer in solution could aggregate and self-assembly into sphere-like polymeric structure.     

Nanoparticle formation from poly(acrylic acid) and oppositely charged peptides

Cationic peptides self assemble upon interacting with sodium salt of oppositely charged polymer, poly(acrylic acid), PAA, giving rise to water-soluble nanoparticles at very low concentration (0.1 mM of PAA). The morphology of these kinds of nanoparticles is mainly governed by the composition of the complexes, which can be expressed as Z+/-, i.e., the ratio of positively charged units to the concentration of anionic units of the polymers present in the system. In the present study, at lower Z+/-, the particles are elongated in shape but adopt spherical shape of 75-100 nm in diameter at higher Z+/- values. We propose that the nanoparticles containing cationic peptides obtained by this methodology can serve as delivery system to enhance the antinociception effect of the chimeric peptide with previously administered doses.     

Grafting of cellulose fibers with poly(epsilon-caprolactone) and poly(L-lactic acid) via ring-opening polymerization

In this study, ring-opening polymerization (ROP) of epsilon-caprolactone (epsilon-CL) and L-lactide (L-LA) has been performed from cellulose fibers. The hydroxyl groups on cellulose act as initiators in the polymerization, and the polymers are covalently bonded to the cellulose fiber. As an attempt to introduce more available hydroxyl groups on the surface, and thereby obtain higher grafting efficiency in the ROP of epsilon-CL and L-LA, unmodified paper was modified with xyloglucan-bis(methylol)-2-methylpropanamide (XG-bis-MPA) and 2,2-bis(methylol)propionic acid (bis-MPA), respectively. The grafted substrates were characterized via Fourier transform infrared spectroscopy (FTIR), contact angle measurement, atomic force microscopy, and enzymatic degradation. The results showed a successful grafting of poly(epsilon-caprolactone) (PCL) and poly(L-lactic acid) (PLLA) from the cellulose fiber surfaces. Furthermore, the results showed an improved grafting efficiency after activation of the cellulose surface with bis-MPA, and showed that the amount of grafted polymer could be controlled by the ratio of added free initiator to monomer.     

Metalloinitiation routes to biocompatible poly(lactic acid) and poly(acrylic acid) stars with luminescent ruthenium tris(bipyridine) cores

Poly(lactic acid) (PLA) and poly(acrylic acid) (PAA) biomaterials with luminescent ruthenium tris(bipyridine) centers couple drug delivery and imaging functions. Hydrophobic [Ru(bpyPLA2)3](PF6)2 (1) was generated from [Ru[bpy(CH2OH)2]3](PF6)2 in bulk monomer using 4-(dimethylamino)pyridine as the catalyst. The bromoesters, [Ru[bpy(CH2OR)2]3](PF6)2, [Ru[bpy(C13H27)2][bpy(CH2OR]2](PF6)2 (4), and [Ru[bpy(PLAOR)2]3]2+ (9) (R=COCBr(CH3)2), served as initiators for tert-butyl acrylate (tBA) polymerization. Conversion of PtBA to PAA via hydrolysis affords water soluble materials, [Ru(bpyPAA2)3]2+ (7) and [Ru[bpy(C13H27)2](bpyPAA2)2]2+ (8) and the amphiphilic star polymer [Ru[bpy(PLA-PAA)2]3)](PF6)2 (11), which is soluble in a H2O/CH3CN (1:1) mixture. Luminescence excitation and emission spectra of the Ru polymers were in agreement with the parent [Ru(bpy)3]2+ chromophore (lambdaex=468, lambdaem=621 nm). Lifetimes of tau approximately 700 ns in both air and nitrogen atmospheres are typical for most materials; however, the amphiphilic star block copolymer 11 is quenched by oxygen to some degree. Thermal analysis shows the expected glass transitions for the polymeric ruthenium complex materials.     

Chitosan membranes modified by contact with poly(acrylic acid)

In this work chitosan membranes modified by contact with poly(acrylic acid) (PAA) aqueous solution at two different temperatures (25 °C and 60 °C) were obtained. The pure chitosan (CS) membranes, as well as those treated with PAA (CSPAA_25 and CSPAA_60) were characterized by FTIR-ATR, water sorption capacity, thermal analysis (TG/DTG), and scanning electron microscopy (SEM). In addition, in vitro permeation experiments were carried out using metronidazol and sodium sulfamerazine aqueous solutions at 0.1% and 0.2% as model drugs. FTIR-ATR results showed the presence of absorption bands of and COO⁻ indicating the formation of a polyelectrolyte complex between chitosan and poly(acrylic acid). The results also indicated that PAA penetrates deeper into the membrane at higher temperature (60 °C), forming a thicker complex layer. Polyelectrolyte complex formation as well as the influence of treatment temperature was confirmed by lower hydrophilicity, higher thermal stability, and lower permeability of the treated membranes. The results show that the methodology used is a simple and very efficient way to drastically change some membrane properties, especially their permeability.     

Patterned biofunctional poly(acrylic acid) brushes on silicon surfaces

Protein patterning was carried out using a simple procedure based on photolithography wherein the protein was not subjected to UV irradiation and high temperatures or contacted with denaturing solvents or strongly acidic or basic solutions. Self-assembled monolayers of poly(ethylene glycol) (PEG) on silicon surfaces were exposed to oxygen plasma through a patterned photoresist. The etched regions were back-filled with an initiator for surface-initiated atom transfer radical polymerization (ATRP). ATRP of sodium acrylate was readily achieved at room temperature in an aqueous medium. Protonation of the polymer resulted in patterned poly(acrylic acid) (PAA) brushes. A variety of biomolecules containing amino groups could be covalently tethered to the dense carboxyl groups of the brush, under relatively mild conditions. The PEG regions surrounding the PAA brush greatly reduced nonspecific adsorption. Avidin was covalently attached to PAA brushes, and biotin-tagged proteins could be immobilized through avidin-biotin interaction. Such an immobilization method, which is based on specific interactions, is expected to better retain protein functionality than direct covalent binding. Using biotin-tagged bovine serum albumin (BSA) as a model, a simple strategy was developed for immobilization of small biological molecules using BSA as linkages, while BSA can simultaneously block nonspecific interactions.     

Synthesis of graft copolymer (CgOH-g-AGA): Physicochemical properties, characterization and application

A graft copolymer of κ-carrageenan and 2-acrylamidoglycolic acid (CgOH-g-AGA) was synthesized via free radical polymerization initiated by potassium peroxymonosulphate/malonic acid redox pair. For affording maximum percentage of grafting, optimum conditions were determined by varying the concentrations of κ-carrageenan, 2-acrylamidoglycolic acid, potassium peroxymonosulphate, malonic acid, hydrogen ion, time and temperature. The swelling, metal ion uptake and flocculation studies were investigated with water, three metals (Ni(2+), Pb(2+) and Zn(2+)) solutions, coal (coking and non-coking) suspensions, respectively. Both, polymer backbone and its corresponding graft copolymer samples were characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis.     

Preparation and PCR-amplification properties of a novel amphiphilic poly(N-vinylpyrrolidone) (PVP) copolymer

A novel amphiphilic copolymer, P(NVP-co-TrpAMT) (9) was prepared, comprising hydrophilic N-vinylpyrrolidone (NVP; 8) and hydrophobic 'N-[(tert-butoxy)carbonyl]tryptophanamido-N'-methacryl thiourea' (TrpAMT; 7) segments. The amphiphilic copolymer 9 was characterized by (1)H-NMR, GPC-MALLS, TEM, and MTT assay. It has a critical micelle concentration (cmc) of 45.7 mg/l in aqueous solution, and good biocompatibility in vivo. According to TEM, the polymer is mostly present as spherical micelles in water, with a diameter of ca. 60-90 nm. In the presence of 0.1 mug/ml of 9, the PCR amplification of the GC-rich beta-actin was efficiently enhanced. Also, the fluorescence intensity of the reporter dye SYBR Green I was increased by 26% at the 14th cycle during real-time PCR of plasmid pUC18 DNA.     

Superabsorbent hydrogel composite made of cellulose nanofibrils and chitosan-graft-poly(acrylic acid)

Superabsorbent hydrogel composites based on cellulose nanofibrils and chitosan-graft-poly(acrylic acid) copolymer were developed in this work. The FTIR data showed that the copolymerization and the composite formation reaction were successfully performed. In addition, the XRD pattern indicated that the nanofibrils crystallinity was as high as 90%. A 2⁴⁻¹ fractional factorial design was employed to evaluate the effect of acrylic acid/chitosan molar ratio, crosslinker, initiator, and filler in the swelling capacity of hydrogel composites. By the analysis of variance (ANOVA), including F-test and P-values, it was found that the crosslinker and filler correspond to 40% and 30% of the evaluated response, respectively. The addition of nanofibrils provided faster equilibrium conditions as well as improved the swelling capacity in ca. 100 units, from 381 to 486. SEM images showed that the addition of nanofibrils into the hydrogel matrix increased the averaged-dimension of porous. Finally, the composites showed responsive behavior in relation to pH and salt solution. Such characteristics make these smart materials suitable for several technological applications.     

Immobilization of urease on gelatin — poly (HEMA) copolymer preparation and characterization

Urease was immobilized onto gelatin-poly (HEMA) copolymer by covalent linkage. Maximum amount of urease was immobilized onto the support at a pH of 8.5. The optimal pH of the immobilized urease was similar to that of free urease; the optimal temperature showed an increase of 10 °C over the free enzyme. The stability of the immobilized urease for a range of pH, temperature and shelf life was greater than the corresponding values for the free enzyme. The same result was obtained for k _m also.Grateful acknowledgement is made to CSIR, Govt. of India for the research associateship conferred on Dr. M. Chellapandian which helped the progress of this piece of research investigation.