Study of the thermal degradation of acrylic copolymers

The thermal degradation of the following copolymers prepared by radical polymerization: acrylonitrile–butyl acrylate–vinylidene chloride, acrylonitrile–butyl acrylate–vinylidene chloride–styrene, and acrylonitrile–methacrylic acid–vinylidene chloride–styrene was investigated. The techniques of thermogravimetry and differential thermal analysis were used. The IR spectra of degradated copolymers are discussed.     

Alginate grafted with poly(ε‐caprolactone): effect of enzymatic degradation on physicochemical properties

The paper discusses the enzymatic behaviour of a series of copolymers composed of alginate grafted with poly(ε‐caprolactone) (PCL) of various lengths and degrees of substitution. The study is focused on viscosity measurements and pyrene probe fluorescence with or without two enzymes: alginate lyase, which breaks the alginate backbone; and esterase, which breaks PCL pendent groups. Alginate lyase is inactive at pH = 3.8 and degrades quickly all copolymers at pH = 6.3. The degradation is not complete and is slowed down by the presence of PCL. Esterase degrades only copolymers with long pendent PCL groups. It has no effect on copolymers when PCL has a length of 530 g mol^?1. These systems are good candidates for controlled release of drugs using an enzymatic method. Copyright © 2012 Society of Chemical Industry     

Printable Hydrogels Based on Alginate and Halloysite Nanotubes

The design of hydrogels for the controlled release of active species is an attractive challenge. In this work, we prepared hybrid hydrogels composed of halloysite nanotubes as the inorganic component, and alginate as the organic counterpart. The reported procedure allowed us to provide the resulting materials with a peculiar wire-like shape. Both optical and scanning electron microscopy were used to characterize the morphological properties of the hydrogel wires, whose diameters were ca. 0.19 and 0.47 mm, respectively. The possibility to be exploited as drug delivery systems was carried out by loading the nanoclay with salicylic acid and by studying the release profiles. Thermogravimetric experiments showed that the amount of encapsulated drug was 4.35 wt%, and the salicylic acid was thermally stabilized after the loading into the nanotubes, as observed by the shift of the degradation peak in the differential thermograms from 193 to 267 °C. The kinetics investigation was conducted using UV–Vis spectrophotometry, and it exhibited the profound effects of both the morphology and dimensions on the release of the drugs. In particular, the release of 50% of the payload occurred in 6 and 10 h for the filiform hydrogels, and it was slower compared to the bare drug-loaded halloysite, which occurred in 2 h. Finally, an induction period of 2 h was observed in the release profile from the thicker sample.     

重组人粒细胞-巨噬细胞集落刺激因子壳聚糖-海藻酸钠微囊的制备

目的以壳聚糖和海藻酸钠为原料,制备重组人粒细胞-巨噬细胞集落刺激因子(rhGM-CSF)微囊,探讨开发口服蛋白多肽类药物的可行性。方法以rhGM-CSF为药物模型,通过壳聚糖与海藻酸钠聚电解质的络合反应制备rhGM-CSF壳聚糖-海藻酸钠微囊,观察微囊的形态大小,测定其包封率,不同pH值下的膨胀度和体外释放率。结果制备的rhGM-CSF壳聚糖-海藻酸钠微囊呈均匀、完整的圆球形,平均直径1mm左右;包封率达80%以上;在模拟肠液(磷酸盐缓冲液,pH7.4)中浸泡3h,膨胀度可达600%,药物释放率达85%以上。结论壳聚糖-海藻酸钠微囊具有肠溶控释作用,有望成为rhGM-CSF等蛋白类口服药物的控释载体。     

Preparation and characterization of pH‐sensitive microparticles based on polyelectrolyte complexes for antibiotic delivery

pH‐sensitive microparticles formed by combination of a synthetic copolymer and sodium alginate in presence of calcium chloride were prepared in mild conditions for specific water‐soluble drug delivery. The copolymers of acryloxyethyl‐trimethylammonium chloride and N‐vinyl‐2‐pyrrolidone were synthesized by radical polymerization in aqueous solution at 60°C using sodium persulfate as initiator. Fourier transform infrared spectroscopic characterization confirmed the structure of the copolymers and their compositions were determined by potentiometric method. Scanning Electron Microscopy study revealed that microparticles have a rough morphology with size ranging from 450 to 800 µm as measured by optical microcopy. Cefotaxime as a model drug was encapsulated in the microparticles to evaluate the in vitro release behavior under different pH conditions. At physiological temperature, the amount of drug released increased with increasing pH. The amount of drug release from microparticles after 24 h (84%) was more extensive in simulated intestinal fluid when compared with acidic pH environment (20%). These preliminary results suggest that the new microparticles can be used as good candidate for oral drug controlled release in the treatment to colon diseases. POLYM. ENG. SCI., 55:981–987, 2015. © 2014 Society of Plastics Engineers     

Swelling Behavior of Calcium–Ions Crosslinked Bipolymeric Sodium Alginate–Lignosulphonic Acid Blends

A series of blends based on lignosulfonic acid (LSA) and sodium alginate (NaAlg) were prepared with varying proportions of NaAlg and LSA using a solution-casting method. The swelling /degradation behavior of blends was studied so that they can be used for gastrointestinal drug delivery. Effect of crosslinking, pH, alginate content, and treatment with strong acid on swelling properties of the blends was investigated. It was found that blends show pH-sensitive swelling and show less water uptake due to crosslinking, while crosslinking is reduced in the presence of strong acid. Thus these blends offer their strong candidature for possible use in drug delivery.     

Alginate–chitosan composite hydrogel film with macrovoids in the inner layer for biomedical applications

Making of a layered composite using two biopolymer gels with regularly aligned voids in the inner layer is described in this article. Calcium alginate constituted the inner layer, within which voids of 500 μm diameter were embedded in monolayer or in multiple layers using a fluidic device for bubbling. The chitosan without any additional crosslinker was used to form the outer layer. The layered structure enabled compartmentalization of drug hold-up, and differential release rates. These aspects were reviewed using bovine serum albumin and vitamin B₁₂ as model solutes. The presence of voids at the inner layer of alginate increased the uptake, raising the level of absorptivity to more than 4000%. The composite film could hold two solutes at a time. The one, held inside the alginate layer started releasing only after 1 h of dipping in the release media. The adhesive strength between layers and the response of the composite film to compressive deformation are studied here. The effect of single or multiple layers of voids in the inner layer is reviewed. The slowing of degradation rate due to chitosan-encapsulation is experimentally determined. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47599.     

Synthesis and properties of polycarbonate copolymers of trimethylene carbonate and 2‐phenyl‐5,5‐bis(hydroxymethyl) trimethylene carbonate

The polycarbonate copolymers poly[trimethylene carbonate‐co‐2‐phenyl‐5,5‐bis(hydroxymethyl) trimethylene carbonate] [P(TMC‐co‐PTC)] were synthesized by the ring‐opening polymerization of trimethylene carbonate (TMC) and 2‐phenyl‐5,5‐bis(hydroxymethyl) trimethylene carbonate (PTC) with tin(II) 2‐ethylhexanoate and aluminum isopropoxide as the catalysts. These copolymers were further reduced by a palladium/carbonate (Pd/C; 10%) catalyst to produce partly deprotected copolymers. These two types of copolymers were characterized by ¹H‐NMR, Fourier transform infrared spectroscopy, UV spectroscopy, gel permeation chromatography, differential scanning calorimetry, and an automatic contact angle meter. The influences of the feed molar ratio of the monomers, the catalyst concentration, the reaction time, and the reaction temperature on the copolymerization process were also studied. The copolymerization of the TMC and PTC monomers was a nonideal copolymerization, and the copolymerization reactivity ratio of TMC was higher than that of PTC. In vitro degradation tests indicated that the partly deprotected copolymers possessed faster degradation rates and more hydrophilicity than the corresponding unreduced copolymers. Moreover, the degradation of these two type copolymers increased when the pH value of the buffer solutions decreased. In vitro drug‐release experiments showed that these two types of copolymers had steady drug‐release rates and good controlled release properties. Moreover, the partly deprotected copolymers had faster drug‐release rates than the corresponding unreduced copolymers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and Properties of Drug-Loaded Chitosan-Sodium Alginate Complex Membrane

Chitosan, sodium alginate and berberine complex membranes were prepared. The structure and properties of the drug-loaded membrane were studied using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric and differential thermal analysis (DTA). The drug-release property of membranes with different ratios of chitosan and sodium alginate was also investigated. The results show that when chitosan and sodium alginate were mixed in weight ratio of 5:1, a polyelectrolyte complex film was formed and exhibited better thermal stability and stronger control ability over drug release.     

基于苯基乙烯基酮双亲性嵌段物的光敏延时释药乳剂

聚苯基乙烯基酮（PPVK）在光照下能够发生主链断裂,基于这一特性,本文利用可逆加成-断裂链转移聚合（RAFT）以丙烯酸二甲氨基乙酯（DMAEA）和丙烯酸异辛酯（2-EHA）分别作为亲水性单体和疏水性单体,制备了双亲性三嵌段共聚物PDMAEA-b-PPVK-b-P（2-EHA）,并利用该双亲性嵌段物作为乳化剂制备了油酸乙酯为环保油相的可光控延时释放的油包水（W/O）型农药乳剂。对乳液的制备稳定性、光敏感特性以及光控药物释放特性进行了研究。结果表明,在油相与水相体积比为2∶1、嵌段物亲水段与亲油段聚合度之比为1∶5、嵌段物添加量为0.03g/mL且内水相pH=5时,制得的乳液具有良好的稳定性;在紫外光照下,乳液能够很快发生破乳;草甘膦药物释放实验表明,乳液的药物释放表现出光控特性,紫外光照25min后,水相药物草甘膦释放率达90%左右。     

Monomer reactivity ratios in UV-initiated free-radical copolymerization reactions

The homopolymers of styrene (S) and vinyl acetate (VA) and their copolymers were prepared in bulk by ultraviolet (UV)-radiation-initiated free-radical polymerization with azobisisobutyronitrile (AIBN) as an initiator. The reacitivity ratios for these copolymerizations were determined by analyzing the monomer content in the copolymers by UV spectroscopy. The same method was extended to other copolymers of styrene such as styrene–methyl methacrylate and styrene–ethyl acrylate. A new analysis method was developed to measure reactivity ratios. For this purpose, UV light was used as a photochemical initiator and UV absorption spectroscopy was used for the determination of the instantaneous composition of copolymers. Nuclear magnetic resonance (NMR) was used to calculate percent conversion. © 1995 John Wiley & Sons, Inc.     

Multiblock copolymers by polymeric initiators via free radical mechanism

Polymeric peroxycarbamate initiators containing polyazoester or polyethylene adipate blocks were synthesized. They can be used to prepare multiblock copolymers by radical polymerization in a procedure involving several steps. Bulk and solution polymerizations are suitable techniques in these steps. The polymerization of styrene with these initiators was investigated over a wide range of conversion. Longer polymerization times led to an expected decrease in peroxygen contents of the active polystyrenes. Styrene/methyl methacrylate/n-butyl methacrylate, polyethylene adipate/styrene/methyl methacrylate, polyethylene adipate/styrene/methyl methacrylate/n-butyl methacrylate and polyethylene adipate/styrene/methyl methacrylate/acrylonitrile multiblock copolymers were obtained in this way.     

海藻酸微胶囊的制备及在药物控释中的研究进展

海藻酸具有相对温和的凝胶条件与良好的生物相容性 ,已广泛应用于药物缓释与生物医学工程。综述了海藻酸微胶囊的制作方法、增加海藻酸微囊的稳定性与控制物质扩散的主要方法及海藻酸凝胶在药物控释研究中的进展     

Preparation of Magnetic pH-Sensitive Film With Alginate Base for Colon Specific Drug Delivery

The aim of this work was to prepare alginate base film and its properties and application in drug delivery field. In order to achieve this, naproxen as a drug and magnetic nanoparticles were placed into the films. Sodium alginate could be crosslinked and form a gel under extremely mild and environmentally friendly conditions without using toxic solvents and reactants. The polymeric films were analyzed by DSC, SEM, and FT-IR spectroscopy. The in vitro release profiles were established separately in both enzyme-free simulated gastric (pH 1) and intestinal fluids (pH 7.4).     

Effect of silicon comonomers on thermal degradation of polystyrene

The thermal degradation of the following organosilicon copolymers: styrene–vinylmethyl-diacetoxysilane, styrene-2-methacryloyloxypropoxytrimethyl silane, styrene–(dimethyl) siloxane–methylvinylsiloxane) diol and hexamethyl cyclotrisiloxane–styrene–hexamethyl cyclotrisiloxane was investigated. The techniques of thermogravimetry, thermomechanical analysis, and differential scanning calorimetry (DSC) were used. The initial decomposition temperature for all the copolymers except styrene–siloxane block copolymers was less than that for polystyrene irrespective of the nature of the silicon comonomer. Integral procedural decomposition temperature of copolymers was higher than that for polystyrene except styrene-2-methacryloyloxy propoxytrimethyl silane copolymers which were showing lower (IPDT) values. Styrene–siloxane copolymers were found to be most thermally stable. Variation in the glass transition temperature and probe displacement under stress is related to the polarity of the silicon moiety in the styrene copolymers.     

Bioinspired photo-degradable amphiphilic hyperbranched poly(amino ester)s: Facile synthesis and intracellular drug delivery

A novel amphiphilic photo-degradable hyperbranched polymer was reported at the first time. The hyperbranched o-nitrobenzyl containing poly(amino ester)s (HPAE) were prepared by one-pot Michael addition polymerization. The photo-induced degradation of hyperbranched poly(amino ester)s was confirmed by gel permeation chromatography (GPC) and UV-vis spectra. Bioinspired phosphorylcholine grafted HPAE (HPAE-PC) was synthesized via thiol-ene click chemistry. HPAE-PC can self-assemble to micelles and the micelles could be disassembled under UV irradiation because of the photo-degradation of HPAE. HPAE-PC micelles were used to load anticancer drug Doxorubicin (DOX). In vitro drug release studies showed that the release of DOX was much faster in the presence of UV irradiation than that without UV irradiation. The fluorescence microscope results indicated that DOX-loaded micelles exhibited faster drug release in A549 cells after UV irradiation. Moreover, the DOX-loaded HPAE-PC micelles under UV irradiation exhibited better anticancer activity against A549 cells than that of the nonirradiated ones. The novel amphiphilic photo-degradable hyperbranched polymers can be used to construct spatiotemporal on-demand drug delivery system for cancer therapy.     

海藻酸盐/壳聚糖复合微球的制备及其控制释放作用

采用喷雾干燥法将活性成分包载到海藻酸钠微凝胶中,再经钙离子和壳聚糖交联得到复合微球。以维生素B₂为模型药物探讨了微球的控制释放效果和机理。扫描电镜分析表明海藻酸钠微凝胶经复合交联后形成了团聚体结构。与单一钙离子交联的海藻酸盐微球相比,复合微球对维生素B₂释放更慢,半数释放时间(t₅₀)延长约6倍,且交联时间越长、交联剂用量越高,维生素B₂释放越慢。当载药量介于16.0%～35.6%时,维生素B₂释放时间达24 h以上,释放过程主要受费克扩散控制。     

AB‐ and ABC‐type di‐ and triblock copolymers of poly[styrene‐block‐(ε‐caprolactone)] and poly[styrene‐block‐(ε‐caprolactone)‐block‐lactide]: synthesis,characterization and thermal studies

Polystyrene terminated with benzyl alcohol units was employed as a macroinitiator for ring‐opening polymerization of ε‐caprolactone and L ‐lactide to yield AB‐ and ABC‐type block copolymers. Even though there are many reports on the diblock copolymers of poly(styrene‐block‐lactide) and poly(styrene‐block‐lactone), this is the first report on the poly(styrene‐block‐lactone‐block‐lactide) triblock copolymer consisting of two semicrystalline and degradable segments. The triblock copolymers exhibited twin melting behavior in differential scanning calorimetry (DSC) analysis with thermal transitions corresponding to each of the lactone and lactide blocks. The block derived from ε‐caprolactone also showed crystallization transitions upon cooling from the melt. In the DSC analysis, one of the triblock copolymers showed an exothermic transition well above the melting temperature upon cooling. Thermogravimetric analysis of these block copolymers showed a two‐step degradation curve for the diblock copolymer and a three‐step degradation for the triblock copolymer with each of the degradation steps associated with each segment of the block copolymers. The present study shows that it is possible to make pure triblock copolymers with two semicrystalline segments which also consist of degradable blocks. Copyright © 2009 Society of Chemical Industry     

Characterization and thermal properties of poly(n‐butyl acrylate‐g‐styrene) graft copolymers

Poly(butyl acrylate‐g‐styrene) graft copolymers were prepared by free‐radical polymerization using a polystyrene macromonomer carrying a methacryloyloxy group at the chain end and they were characterized by size‐exclusion chromatography, and Fourier transform infrared spectroscopy. Glass transition temperatures and degradation behavior were determined by thermal analysis. Only a single glass transition temperature was observed for the resulting graft copolymers, indicating the miscibility between the poly(styrene) phase and poly(butyl acrylate) (pBA) phase in the graft copolymer. The incorporation of polystyrene segments in the graft copolymer improved the thermal stability of pBA and enhanced the apparent activation energy for the thermal degradation of pBA. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 783–789, 2001     

Characterization and possible agricultural application of polyacrylamide/sodium alginate crosslinked hydrogels prepared by ionizing radiation

Polyacrylamide/sodium alginate (PAAm/Na‐alginate) crosslinked copolymers were prepared by using electron beam irradiation. The gel content and the swelling behavior of the obtained copolymers were investigated. The thermal and morphological properties of the prepared copolymers were studied using thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The thermal stability of PAAm significantly changed when mixed with Na‐alginate. The addition of PAAm/Na‐alginate copolymer in small quantities to sandy soil increased its ability to retain water. The growth and other responses of the faba bean plant cultivated in a soil treated with PAAm and PAAm/Na‐alginate copolymer were investigated. The growth of the bean plant cultivated in a soil containing PAAm/Na‐alginate was better than that cultivated in soil treated with PAAm. The most significant difference between the PAAm and its alginate copolymer is that the latter partially undergoes radiolytic and enzymatic degradation to produce oligo‐alginate, which acts as a plant growth promoter. The increase in faba bean plant performance by using PAAm/Na‐alginate copolymer suggested its possible use in the agriculture field as a soil conditioner, providing the plant with water as well as oligo‐alginate growth promoter. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3572–3580, 2006