Adsorption of Methylene Blue on Poly (Methacrylic Acid) Modified Chitosan and Photocatalytic Regeneration of the Adsorbent

The preparation of poly(methacrylic acid) modified chitosan microspheres (PMAA-GLA-CTS) and its application for the removal of cationic dye, methylene blue (MB), in aqueous solution in a batch system were described. The modified chitosan was characterized using FTIR and XPS analysis. The effects of the pH of the solution, contact time, and initial dye concentration were studied. The adsorption capacity of the microspheres for MB increased significantly after the modification as a large number of carboxyl groups were introduced. The equilibrium process was better described by the Langmuir rather than the Freundlich isotherm. According to the Langmuir equation, the maximum adsorption capacity was 1 g · g^?1 for MB. Kinetic studies showed better correlation coefficients for a pseudo-second-order kinetic model, confirming that the sorption rate was controlled by a chemisorption process. Photocatalytic regeneration of spent PMAA-GLA-CTS using UV/TiO₂ is effective. Further, the regenerated PMAA-GLA-CTS exhibits 90% efficiency for a subsequent adsorption cycle with MB aqueous solutions.     

Experimental problems in the application of UV/visible based methods as the quantification tool for the entrapped/released insulin from PLGA carriers

BACKGROUND: Controlled release of medicaments from biodegradable polymers remains the most convenient way for their sustained release. Although a number of articles have been published, experimental work involving the preparation of polymer‐based carriers and release procedures are not described with sufficient level of detail to allow other researchers to reproduce the experiments and to compare published results with their own. In this contribution the experimental background of the entrapment and release of insulin from PLGA carriers is described and the problems found at each step related to UV/Visible method used to quantify them are addressed in detail. RESULTS: The quantification of entrapped insulin by UV/visible methods was affected by aggregation. The design of the release experiment influenced the results regarding the entrapment efficiency (EE) and the maximum percentage of released insulin. It was also found that the presence of colloidal polymeric particles, insufficient centrifugation times and the kind of solvent used in the release test might lead to mistakes in the percentage of liberated insulin when UV/visible based methods are employed. CONCLUSIONS: This contribution demonstrates that serious discrepancies in the EE and percentage of released protein may arise if some key experimental factors are not taken into account. Therefore, the analysis presented here tries to point out important aspects of this topic currently not reported, unnoticed or not properly analyzed in the open literature. The results are useful for the entrapment of any protein on any polymeric device using UV/visible based methods to quantify them. Copyright © 2009 Society of Chemical Industry     

Heterogeneous and homogeneous structure dextran–poly(methacrylic acid) interpenetrating network hydrogels: synthesis and an application study

pH‐sensitive dextran–poly(methacrylic acid) (Dext–pMeAc) full interpenetrating network hydrogels (INHs) were prepared by simultaneous radical polymerization of methacrylic acid monomer (MeAc) and Dext polymer chains in the presence of N,N‐methylenebisacrylamide (MBA) as crosslinker in aqueous solution. These hydrogels were investigated as a drug carrier. The influence of MeAc and MBA contents in the network hydrogels on the swelling behaviour and mechanical strength of prepared Dext–pMeAc INHs was evaluated. Dext–pMeAc INHs were characterized by Fourier transform IR spectroscopy, and kinetic swelling measurements were carried out in deionized water and in simulated gastric fluids (pH 1.1 and pH 7.4). Dext–pMeAc/1‐1, Dext–pMeAc/3‐1 and Dext–pMeAc/5‐1 hydrogels with molar ratios of n_Dext/n_MeAc = 10 and n_MBA/n_Dext = 10, 30 and 50 respectively showed a core–shell structure when they swelled. This phenomenon was not observed in Dext–pMeAc/5‐2, Dext–pMeAc/5‐3 and Dext–pMeAc/5‐5 hydrogels containing a higher amount of Dext in the gels. The swelling data proved the formation of INHs with pH‐sensitive behaviour. A drug release study was performed using Rhodamine 6G fluorescent dye as a model hydrophilic bioactive molecule. The in vitro release rate of Rhodamine 6G from Dext–pMeAc/5‐3 hydrogel was dependent on the pH of the release medium. Copyright © 2012 Society of Chemical Industry     

Gamma radiation synthesis and swelling properties of hydrogels based on poly(ethylene glycol)/methacrylic acid (MAc) mixtures

In this work, gamma radiation was used to prepare hydrophilic hydrogels based on different mass ratios of poly(ethylene glycol) (PEG) and methacrylic acid (MAc) monomer. The thermal stability of hydrogels was characterized thermogravimetric analysis (TGA). The effect of temperature and pH, as external environments, on the equilibrium swelling of PEG/MAc hydrogels was also studied. The results showed that the gel fraction of PEG/MAc hydrogels is lower than that of PMAc hydrogel, in which the gel fraction of PMAc hydrogel was decreased greatly with increasing the mass ratio of PEG polymer in the initial solutions. The results showed that PEG/MAc hydrogels reached the equilibrium swelling state in water after 6 hours. It was found that the equilibrium swelling of PEG/MAc hydrogels displayed a transition change within the temperature range 30–40°C. This change in equilibrium swelling was illustrated by differential scanning calorimetry (DSC). However, it was observed that the equilibrium swelling of PEG/MAc hydrogels increases progressively with increasing the pH value from 4 up to 8. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Manipulating drug release from tridimensional porous substrates coated by initiated chemical vapor deposition

In the recent years, modern wound dressings have attracted much interest to accelerate wound healing processes with the topical delivery of drugs directly on wounds having a significant effect on wound rehabilitation. The objective of this study was to develop a model dressing that would not only provide wound protection from the environment but might also provide the possibility to keep it moist and deliver a drug for potential speeding the healing process. Poly(ethylene terephthalate), cotton fabrics, and polycaprolactone (PCL) nanofibers were used as different tridimensional porous substrates, loaded with a model drug, clotrimazole. The results show that the chemical structure and surface area to volume ratio of the pristine substrates affect the drug release profile. Coating of such substrates by hydrogels poly(2-hydroxyethyl methacrylate) (p-HEMA) and poly(methacrylic acid) (p-MAA) was successfully achieved by initiated chemical vapor deposition. This method was chosen because it is gentle and solventless and most important it can coat free areas within the three-dimensional structures. Scanning electron microscopy results revealed that p-HEMA and p-MAA conformally coated the fibers of the substrates. Moreover, drug release experiments showed that p-HEMA and p-MAA coatings provide barriers preventing sudden drug release. In conclusion, our results indicated the possibility of fabricating dressings containing a drug with tunable drug release profile depending on several parameters even though a strong porous structure exists. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47858.     

Isopropyl Amino Acid Esters Ionic Liquids as Vehicles for Non-Steroidal Anti-Inflammatory Drugs in Potential Topical Drug Delivery Systems with Antimicrobial Activity

New derivatives of non-steroidal anti-inflammatory drugs were synthesized via conjugation with L-amino acid isopropyl esters. The characteristics of the physicochemical properties of the obtained pharmaceutically active ionic liquids were determined. It has been shown how the incorporation of various L-amino acid esters as an ion pair affects the properties of the parent drug. Moreover, the antimicrobial activity of the obtained compounds was evaluated. The proposed structural modifications of commonly used drugs indicate great potential for use in topical and transdermal preparations.     

间苯二甲酸改性聚醚酯弹性体的合成与表征

用间苯二甲酸(IPA)作为改性剂,对以对苯二甲酸二甲酯(DMT),1,4–丁二醇(BDO),聚四氢呋喃醚(PTMG)和抗氧剂1010为原料以及钛酸丁酯为催化剂合成的软硬段为7∶3的聚醚酯弹性体进行改性,以提高其纤维的低温回弹性能。通过改变IPA与DMT的物质的量比(1∶5~1∶15),成功地合成了一系列的IPA改性聚醚酯弹性体(PBITG–1~PBITG–5),并对其结构、热性能、力学性能和纤维回弹性能进行了测试和表征。通过对IPA改性聚醚酯弹性体的傅立叶变换红外光谱和核磁谱图分析可知,成功地合成了IPA改性聚醚酯弹性体。从差示扫描量热测试结果分析得知,随着IPA含量的降低,所合成的IPA改性聚醚酯弹性体的熔点逐渐增加。热重分析结果表明,不同IPA含量的聚醚酯弹性体都具有良好的热稳定性能,起始分解温度都高于365℃。通过单纤强力仪测试表明,同一拉伸倍数下,随着IPA含量的减少,聚醚酯弹性体纤维的断裂强度和断裂伸长率都有所增加。低温回弹性能测试结果表明,IPA的加入的确能提高聚醚酯弹性体纤维的低温回弹性能,其中,PBITG–1纤维拉伸1倍时对应的低温回弹率最大,为97.92%。     

Synthesis,characterization, and fluorescence properties of lanthanide complexes with poly(styrene‐co‐methacrylic acid)

A series of new complexes of poly(styrene‐co‐methacrylic acid) with Ln(III) (Ln = La, Eu, Tb) were synthesized and well characterized by means of elemental analysis, FTIR, differential scanning calorimetric (DSC) analysis, TG‐DTA analysis, X‐ray diffraction (XRD), and fluorescence determination. The elemental analysis and FTIR studies showed that a large part of carboxylic groups on the side chain of the copolymer are coordinated with Ln(III) ions. The TG‐DTA and DSC analysis results indicated that the complexes have good thermal stability. XRD experiments showed that copolymers and the complexes are amorphous. Among these complexes, Eu(III) complexes and Tb(III) complexes exhibit characteristic fluorescence with comparatively high brightness and good monochromaticity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Self‐Healing Behavior of Blends Based on Ionomers with Ethylene/Vinyl Alcohol Copolymer or Epoxidized Natural Rubber

The effect of blending on the self‐healing behavior of an ethylene/methacrylic acid copolymer ionomer is investigated. Binary EMNa/EVA and EMNa/ENR blends are studied by ballistic puncture tests. In the composition range explored (15–50 wt% of EVA and ENR), the self‐healing characteristics decrease with increasing amount of EVA but are maintained in the whole range for EMNa/ENR blends. The bullet impact zones were observed using OM. Tensile tests showed that the blending process gives the opportunity to tune the mechanical characteristics without significant loss in the self‐healing properties, particularly in EMNa/ENR blends. Component compatibility, blend morphology and thermal properties were studied using DSC, SEM, and DMTA. Molecular interactions between the phases in the blends are discussed.

     

Biocomposites of Epoxidized Natural Rubber/Poly(lactic acid) Modified with Natural Fillers (Part I)

The study aimed to prepare sustainable and degradable elastic blends of epoxidized natural rubber (ENR) with poly(lactic acid) (PLA) that were reinforced with flax fiber (FF) and montmorillonite (MMT), simultaneously filling the gap in the literature regarding the PLA-containing polymer blends filled with natural additives. The performed study reveals that FF incorporation into ENR/PLA blend may cause a significant improvement in tensile strength from (10 ± 1) MPa for the reference material to (19 ± 2) MPa for the fibers-filled blend. Additionally, it was found that MMT employment in the role of the filler might contribute to ENR/PLA plasticization and considerably promote the blend elongation up to 600%. This proves the successful creation of the unique and eco-friendly PLA-containing polymer blend exhibiting high elasticity. Moreover, thanks to the performed accelerated thermo-oxidative and ultraviolet (UV) aging, it was established that MMT incorporation may delay the degradation of ENR/PLA blends under the abovementioned conditions. Additionally, mold tests revealed that plant-derived fiber addition might highly enhance the ENR/PLA blend’s biodeterioration potential enabling faster and more efficient growth of microorganisms. Therefore, materials presented in this research may become competitive and eco-friendly alternatives to commonly utilized petro-based polymeric products.     

Preparation and Characterization of Novel Food Packaging Materials Based on Biodegradable PCL/Ag-Kaolinite Nanocomposites with Controlled Release Properties

Food packaging materials based on biodegradable poly(ε-caprolactone)/Ag-Kaolinite nanocomposites with controlled release properties were successfully prepared via solvent casting method. X-Ray Diffraction, UV-visible Spectroscopy and Transmission Electron Microscopy results revealed the formation of mixed intercalated-exfoliated structures with a random dispersion of spherical Ag nanoparticles. PCL/Ag-KT films have showed a significant improvement in their barrier and antibacterial properties. The potential of the silver ion release from the PCL/Ag-Kt films to an aqueous medium was measured by Atomic Absorption Spectroscopy. The results exhibited a gradual increase of the amount of silver ions released. The release’s mechanism was mainly governed by the diffusion process.     

Control of biodegradability of poly(3‐hydroxybutyric acid) film with grafting acrylic acid and thermal remolding

Radiation‐induced graft polymerization of acrylic acid (AAc) on poly(3‐hydroxybutyric acid) (PHB) film was carried out and the resulting film was thermally‐remolded. The PHB films grafted with AAc (PHB‐g‐AAc) having a degree of grafting higher than 5% completely lost the enzymatic degradability. The enzymatic degradability of the grafted film was recovered by thermal remolding. The highest enzymatic degradation rate was observed at degree of grafting of 10% after thermal remolding. The PHB‐g‐AAc films and thermally‐remolded PHB‐g‐AAc films were characterized by contact angle and differential scanning calorimetry. The enzymatic degradability of PHB‐g‐AAc films was lost by the grafted AAc, which covered the surface of PHB film. The acceleration of enzymatic degradation in the remolded PHB‐g‐AAc films was mainly caused by decrease of crystallinity of PHB by dispread of grafted AAc during thermal remolding. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3856–3861, 2006     

Functionalization of Polyacrylic Acid with Tetrahydroxybenzene via a Homolytic Pathway: Application to Metallic Adsorption

Poly(acrylic acid) (PAA) was synthesized and chemically modified with 1,2,4,5-tetrahydroxybenzene (THB) or benzene-1,2,4,5-tetrol applying the reaction conditions of Minisci. A degree of modification of as high as 55% was obtained under optimal conditions: temperature of 70–80°C, time of 4 h, and [DHBQ]/[AA] ratio of 1.25. The synthesized PAA and its modified form, THB-PAA, were characterized by UV-visible, FT-IR, and ¹³C NMR spectroscopy. A severe degradation of the modified PAA was observed as revealed by viscometric measurements. The glass transition temperature of THB-PAA was found to be lower than that of pristine PAA, 123 versus 151°C. Potentiometric titrations of PAA and its modification, and their copper (II)-complexed polymers Cu-PAA and Cu-THB-PAA with 0.1 N aqueous NaOH, showed peculiar profiles. Study of copper (II) adsorption by the crosslinked PAA and THB-PAA resins varied with the following parameters: pH, time, temperature, ionic strength, sorbent mass, and initial copper (II) concentration. Optimal copper sorption extents of 5.5 and 23 mg/g for PAA and THB-PAA resins, respectively, were found for a pH of 5.4, a time of 3 h, a temperature of 45°C, and an ionic strength of 0. A new way of crosslinking poly(acrylic acid) and its modified form has been conceived via an oxidative decarboxylation process.     

Intrinsic factor and vitamin B12 complex‐loaded poly[lactic‐co‐(glycolic acid)] microspheres: preparation,characterization and drug release

BACKGROUND: Vitamin B12 is an essential vitamin required by all mammals. Absorption of vitamin B12 is facilitated by binding of intrinsic factor–vitamin B₁₂ complex to specific receptors in the ileum. In humans a deficiency of this vitamin or a lack of intrinsic factor leads to pernicious anaemia. The major objective of the present study was to prepare intrinsic factor–vitamin B12 complex‐loaded poly[lactic‐co‐(glycolic acid)] (PLGA)‐based microparticles and to investigate their release kinetics. RESULTS: PLGA copolymer was synthesized by the ring‐opening polymerization method and characterized using gel permeation chromatography, Fourier transform infrared spectroscopy and ¹H NMR. The glass transition temperature measurement showed a single T_g at 40 °C. The intrinsic factor–vitamin B12 complex‐loaded PLGA microspheres were prepared by a water‐in‐oil‐in‐water double emulsion solvent extraction/evaporation technique. An environmental scanning electron microscopy investigation demonstrated that the PLGA particles had a mean particle diameter of 38 µm. Interestingly, different drug release patterns (bi‐ and triphasic ones) were observed for vitamin B12‐loaded and intrinsic factor–vitamin B12 complex‐loaded microspheres. In contrast to the rapid release of vitamin B12 by itself, in vitro release tests showed that intrinsic factor and vitamin B12 in the complex were released from PLGA microspheres in a sustained manner over 15 days. CONCLUSION: PLGA microspheres can be an effective carrier for the intrinsic factor–vitamin B12 complex. Copyright © 2007 Society of Chemical Industry     

Preparation of chemically crosslinked gels with maleate‐denatured poly(vinyl alcohol) and its application to drug release

Maleate‐denatured poly(vinyl alcohol) (M‐PVA) was crosslinked with heating. The mechanism of crosslinking was studied with several procedures: titration, Fourier transform infrared, and solubility. The carboxyl groups of M‐PVA consisted of carboxylates and a few free carboxyl groups. The crosslink was the ester linkage between hydroxyl and carboxyl groups. Several kinds of M‐PVA tablets were prepared under different conditions: pressures of 200–600 kgf/cm² and grain sizes of 75 (pass) to 250 μm (on). The swelling behavior of these chemically crosslinked tablets was studied in a buffer solution of pH 7.4, mainly at 37°C. Moreover, the effect of temperature from 5 to 50°C and the effect of repeated swell–dry cycles on the behavior of the tablets in a buffer solution [106 μm (on), 200 kgf/cm²] were studied. The release of p‐acetamidophenol from those tablets in the pH 7.4 buffer solution was studied. The different release patterns were due to the differences in the swelling behavior. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1178–1184, 2002; DOI 10.1002/app.10411     

Simplified preparation of low polydispersity,low molecular weight poly(D,L‐lactic acid) by liquid/liquid phase separation for drug delivery systems with discussion of molecular weight characterization

Poly(D ,L ‐lactic acid) (PLA) has been widely used in pharmaceutics and medicine. Low molecular weight (LMW) PLA is especially useful for rapidly degrading biomaterials such as those used for short‐duration drug delivery systems. There is scant information available in the literature regarding the purification and analysis of LMW PLA. In this paper we report (1) a convenient and effective polymer purification/fractionation technique to produce LMW PLA with narrow molecular weight distribution (MWD) and (2) analyses that were used to characterize the molecular weight and MWD of these polymers. A novel, convenient and effective temperature‐induced solution‐phase separation method was developed to produce narrow MWD, LMW (600–2000 g mol^?1) PLA. Molecular weights determined using gel permeation chromatography (GPC) with universal calibration, unlike those determined with the commonly used conventional calibration, showed good agreement with those obtained using several independent direct techniques. The phase separation induced by temperature reduction of a polymer in a single solvent system provided a simple and effective technique to produce narrow MWD, LMW PLA polymers. Additional advantages of this technique are: (1) only one solvent is required; (2) the risk of local complete solid polymer precipitation is eliminated; (3) it is reversible and not dependent on the rate of cooling; and (4) use of chlorinated solvents is avoided. This technology may open up a new opportunity for manufacturing LMW polymers with narrow MWD. We also found that GPC with universal calibration is a more accurate method than GPC with the commonly used conventional calibration for characterizing these polymers, and is straightforward to use especially now that on‐line viscosity detectors are widely available. Copyright © 2010 Society of Chemical Industry     

An Efficient Preparation and Characterization of Nanocomposite Films Based on Poly(vinyl chloride) and Modified ZnO Quantum Dot with an Optically Active Diacid Containing Amino Acid as Coupling Agent

The nanocomposites were manufactured by the incorporation of modified ZnO into the poly(vinyl chloride). ZnO nanoparticles were modified with diacid containing alanine amino acid. Ultrasonic irradiation was used for all process. The PVC/ZnO@DA nanocomposites were investigated by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, UV–visible spectroscopy, thermogravimetric, and mechanical analysis. Results showed the uniform dispersion of particles in the polymer matrix and ZnO@DA nanoparticles in quantum dot size. The optical properties of PVC were affected by the incorporation of modified quantum dot ZnO; also mechanical properties of PVC/ZnO@DA nanocomposites were improved.     

Swelling and drug release profile of poly(2‐ethyl‐2‐oxazoline)‐based hydrogels prepared by gamma radiation‐induced copolymerization

Poly(2‐ethyl‐2‐oxazoline) and acrylic acid were copolymerized in different compositions using γ‐rays‐induced polymerization and cross‐linking to obtain a series of pH‐sensitive hydrogels. The preparation parameters that may affect the copolymerization process such as the feed solution composition and irradiation dose were optimized. Swelling characteristics of the obtained polymeric hydrogels were evaluated. The results show the significant effects of the hydrogel composition, soaking time, and pH on the swelling equilibrium. The diffusion parameters obtained at pH 1 and 7 show the possibility of using the prepared hydrogels in the field of colon‐specific drug delivery systems. Ibuprofen as a model drug was loaded into (poly(2‐ethyl‐2‐oxazoline)/acrylic acid) copolymer hydrogel to investigate their drug release behavior at different pH values. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Melt polycondensation of L‐lactic acid to poly(L‐lactic acid) with Sn(II) catalysts combined with various metal alkoxides

Melt polycondensation of L ‐lactic acid (LA) was examined in the presence of binary catalyst systems consisting of SnCl₂·2H₂O and metal alkoxides as co‐catalysts. Among the co‐catalysts examined, viz (Al(O ⁱPr)₃,Ti(O ⁱPr)₄,Y(O ⁱPr)₃,Si(OEt)₄ and Ge(OEt)₄), Ge(OEt)₄ was found to be the most effective in enhancing the catalytic activity of Sn(II). With an optimized composition of SnCl₂·2H₂O–Ge(OEt)₄, the molecular weight (M_n) of PLLA reached 40 000 Da in a short reaction time (<15 h) at the optimum reaction conditions of 180 °C and 10 Torr. This catalyst system was also superior to the conventional single metal ion catalysts such as Sn(II) in terms of racemization and discolouration of the resultant polymer. The metal alkoxides, added as co‐catalysts, should work as oxo acids that can effectively control the catalytic activity of Sn(II) ion in the direct polycondensation of LA, in a manner similar to that of proton acids. © 2003 Society of Chemical Industry