Synthesis,characterization, and degradation behaviors of poly(D,L-lactide-co-glycolide) modified by maleic anhydride and ethanediamine

In order to improve hydrophilicity and settle the acidity in hydrolysis, a novel ethanediamine (EDA) and maleic anhydride (MAH) modified poly(D,L-lactide-co-glycolide) (PLGA) polymer (EMPLGA) was synthesized. Fourier Transform Infrared Spectrometer (FTIR), Gel Permeation Chromatography (GPC), Nuclear Magnetic Resonance (1HNMR), titration and the water contact angles were employed to characterize the synthesized polymer. The effects of various polymerization conditions on weight average molecular mass (Mw), polydispersity index (PDI) and anhydride content of MPLGA were investigated. The degradation behaviors of PLGA, MPLA and EMPLGA were also studied by observation of the changes of the pH value of incubation medium, molecular weight and weight loss ratio for a time interval of 25 days in-vitro, respectively. The results showed that MPLGA with high anhydride content was successfully obtained by directly ring-opening polymerization and ethanediamine was further grafted onto MPLGA, and there is almost unchanged in Mw between MPLGA and EMPLGA polymers. The introduction of anhydride and amino groups improved the hydrophilicity of PLGA. A uniform degradation of EMPLGA was observed in comparison with an acidity-induced auto-accelerating degradation featured by PLGA and MPLGA. The results revealed that the introduction of ethanediamine into PLGA has weakened or neutralized the acidity of PLGA degradation products.     

Characterization of chloroprene and maleic anhydride copolymer by 13C-NMR spectroscopy and pyrolysis GC/MS

The radical copolymerizations of chloroprene (CP) and maleic anhydride (MAH) were carried out with AIBN in 1,4-dioxane at 60°C. The monomer reactivity ratios were estimated as r₁ (CP) = 0.38 and r₂ (MAH) = 0.07. Microstructures in the copolymer of chloroprene (CP) and maleic anhydride (MAH) were investigated by 75.4 MHz ¹³C-and 300 MHz ¹H-NMR spectroscopies. Resonances were assigned to the monomer sequence dyads CC, CM, and MC (C = chloroprene, M = maleic anhydride). Well resolved fine structure in the ¹³C-NMR spectra showed that 1,2- and 3,4-structural chloroprene units were negligible in the copolymer. The pyrolysis characterization of the copolymer was also investigated by the pyrolysis gas chromatography mass spectrometry (GC/MS). The fragments of CP and MAH monomers and CP-MAH hybrid dimer, CO, and CO₂ were identified after pyrolysis of the copolymer. © 1994 John Wiley & Sons, Inc.     

Biocompatibility properties of composite scaffolds based on 1,4-butanediamine modified poly(lactide-co-glycolide) and nanobioceramics

Three-dimensional biodegradable porous scaffolds play an important role in tissue engineering. The degradable scaffold material, based on 1,4-butanediamine-modified poly(lactide-co-glycolide) (BMPLGA), nano-bioactive glass (NBAG), and nano-β-tricalciumphosphate (β-TCP), was prepared by a solution-casting/salt-leaching method. The biological properties were studied by using cell cytotoxicity, von Kossa staining, alkaline phosphatase activity, hemolytic test, acute toxicity, and genetic toxicity test. The MTT results indicated that the BMPLGA/NBAG-β-TCP materials did not show any cytotoxicity. The result of von Kossa staining showed that the introduction of the NBAG and β-TCP promoted fibroblastic differentiation and improved the mineral deposition of the BMPLGA matrix. In addition, the presence of NBAG and β-TCP in the composite further enhanced the ALP activity in comparison with the sole BMPLGA material. The hemolytic potential showed that the nanocomposite scaffolds were non-hemolytic. The BMPLGA/NBAG-β-TCP scaffolds showed no acute systemic toxicity or mutagenic action. Therefore, the results indicated the BMPLGA/NBAG-β-TCP nanocomposite scaffold could be considered as a potential bone tissue engineering implant.     

A comparison of modifications induced by Li<Superscript>3+</Superscript> and Ag<Superscript>8+</Superscript> ion beams irradiation in poly(lactide-<Emphasis Type="Italic">co</Emphasis>-glycolide) films

Poly(lactide-co-glycolide) (PLGA) films were irradiated by 180 MeV/amu Ag⁸⁺ ions and 50 MeV/amu Li³⁺ ions at different fluences of 5 × 10¹⁰, 5 × 10¹¹ and 1 × 10¹² ions/cm². Modifications of polymer films induced by the swift heavy ions (SHI) irradiation were studied by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR) and UV–Vis spectroscopy. The dominant effect of the SHI beam irradiation is proposed to be chain scission which leads to breakage of polymer chains, followed by hydrogen abstraction. The results from FTIR spectroscopy showed that the intensity of all peaks of the irradiated samples decreased at high fluence of SHI, suggesting PLGA samples significantly degraded at high SHI fluence. The variation in optical band gap energy and Urbach energy with increasing fluence was calculated from UV–Vis spectroscopy and explained in terms of changes occurring in the polymer matrix. X-ray diffraction patterns also show appreciable changes in PLGA at high fluence. FESEM results revealed that the hydrophilicity of the PLGA surface increased with an increase in ion fluence. In this paper the optical, chemical and structural changes with different fluence rates are discussed.     

Photoaddition of maleic anhydride to unsaturated polymers in homogeneous solution,solid polymer–solution,and solid polymer–vapor systems

Photoreactions of maleic anhydride (MAH) with unsaturated olefinic polymers such as 1,2-polybutadiene, 1,4-polybutadiene, block copolymer of styrene and butadiene, polystyrene, poly(styrene-co-isoprene), and poly(styrene-alt-methyl methacrylate) were investigated in air. When the polymers have olefinic unsaturation, the addition of MAH to the polymers in homogeneous solutions proceeded efficiently by a chain mechanism, and the quantum yield of the photoaddition of MAH was greater than unity under irradiation at λ > 310 nm. From the effects of solvent and photosensitizer, a radical chain mechanism involving crosslinking of the polymers by MAH molecules was suggested. Together with the spectroscopic results, the reaction mechanism was discussed. The photoaddition reaction was then applied to the surface photomodification of polymer films. Photoreactions were conducted at the interphase between solid polymer and acetone solution of MAH and also at the interphase between solid polymer and gaseous MAH. Irradiation by a 300-W high-pressure mercury lamp could bring about considerable modification of the surface properties of the polymers, which then show improved wettability and dyeability. From the oxygen permeation experiments, the present interfacial phototreatment was shown to provide a double-layered polymer film in which one side of the film is polar and hydrophilic while the other side is nonpolar and hydrophobic.     

Degradation behavior of electrospun microfibers of blends of poly(lactide-co-glycolide) and Pluronic F-108

Electrospun poly(dl-lactide-co-glycolide) (PLGA) microfibers have been explored as extra cellular matrix mimicking scaffolding systems for tissue engineering application. However, the hydrophobic nature of PLGA can be limiting in terms of protein adsorption. Hence, blending of PLGA with a hydrophilic polymer (Pluronic^®) prior to electrospinning has been explored as a potential strategy to impart hydrophilicity to PLGA microfibers. In this study, PLGA (85/15) was blended with small quantities (0.5-2% w/v) of Pluronic^® F-108 (PF-108) and electrospun into microfibers. Blending of PF-108 demonstrated a significant decrease in the surface hydrophilicity of microfibers as was evidenced by an increase in wetting tension. Surface analysis using XPS indicated the presence of PF-108 in the bulk of the fibers in addition to the surface of the fibers. The results of the water uptake studies indicated that the water uptake capacity and consequential fiber swelling was significantly increased in the presences of PF-108. The in vitro degradation studies demonstrated that the trend in molecular weight loss was not significantly influenced by the presence of small quantities of PF-108. Therefore, blending of PLGA with PF-108 could be an effective technique for surface modification of electrospun PLGA microfibers without compromising on the other advantages of PLGA.     

Synthesis and antitumor activities of alkyl-1,4-butanediamine Pt(II) complexes having seven-membered ring structure

Novel alkyl-1,4-butanediamine Pt(II) complexes having a seven-membered ring structure were synthesized and characterized by fast atom bombardment mass and infrared spectra and elemental analysis. Their antitumor activities in vivo toward lymphoid leukemia L1210 and Lewis lung carcinoma LL were studied in the case where the leaving group was either dichloride or cyclobutane-1,1-dicarboxylate. 1,4-Butanediamine Pt(II) complexes (seven-membered ring) showed higher antitumor activities than those of ethylenediamine Pt(II) (five-membered ring) and 1,3-propanediamine Pt(II) (six-membered ring) complexes toward L1210 for both leaving groups. Alkyl-1,4-butanediamine Pt(II) complexes showed high antitumor activities toward L1210, except for 1,1-dimethyl-1,4-butanediamine Pt(II) complexes. In particular, 2,2-dimethyl-1,4-butanediamine and 2,3-dimethyl-1,4-butanediamine Pt(II) complexes exhibited excellent antitumor activities with T/C% values higher than 300. None of the dichloro Pt(II) complexes showed antitumor activities toward LL, but the cyclobutane-1,1-dicarboxylato Pt(II) complexes, which were moderately active toward L1210 with T/C% values around 200, also showed high antitumor activities toward LL with T/C% values of more than 200. Alkyl-1,4-butanediamine Pt(II) complexes with a seven-membered ring structure were found to be stable and to have antitumor activities in vivo.     

Photoinitiated grafting of maleic anhydride onto polypropylene

The photoinitiated grafting of maleic anhydride (MAH) onto polypropylene with the use of benzophenone (BP) as the initiator has been investigated. In comparison with the process of thermally initiated grafting with peroxide as the initiator, photoinitiated grafting affords a higher grafting efficiency. The efficient photografting sensitized by BP can be explained by two possible mechanistic processes: the sensitization of the formation of the excited triplet state of MAH by BP and electron transfer followed by proton transfer between MAH and the benzopinacol radical, which may operate together. In the former case, the generated MAH excited triplet state abstracts a hydrogen from the polymer substrate to initiate grafting. A rate constant of 3.6 × 10⁹ M ^?1 s ^?1 has been determined by laser flash photolysis for the process of quenching the excited triplet state of BP with ground‐state MAH. In comparison, the rate constant for the quenching of the excited triplet state of BP by hydrogen abstraction has been determined to be 4.1 × 10⁵ M ^?1 s ^?1. In a study of photografting using a model compound, 2,4‐dimethylpentane, as a small‐molecule analogue of polypropylene, the loss of BP was significantly reduced upon the addition of MAH, and this is consistent with the proposed mechanistic processes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1953–1962, 2004     

PLGA/TiO2纳米药物缓释载体的研究

首先利用硅烷偶联剂(KH550)对纳米二氧化钛表面进行预处理,得到氨基改性的二氧化钛,然后与带有高活性端基的丙交酯-乙交酯共聚物(PLGA)反应,制备纳米药物缓释载体PLGA/TiO2有机-无机杂化材料.通过核磁(1H-NMR)、傅里叶变换红外光谱仪(FTIR)、热重分析(TGA)、扫描电子显微镜(SEM)、透射电子显...     

Peroxide-catalyzed grafting of maleic anhydride onto molten polyethylene in the presence of polar organic compounds

The crosslinking of LDPE resulting from reaction with dicumyl peroxide at 180°C is increased in the presence of maleic anhydride (MAH). The presence of electron-donating nitrogen-containing compounds (amides, lactams, disubstituted aromatic amines, and amine oxides), phosphorous-containing compounds (phosphites, phosphates, phosphonates, phosphoramides, and phosphine oxides) and sulfur-containing compounds (sulfoxides, aryl disulfides, and thiazyl disulfides) which inhibit the homopolymerization of MAH but not that of methyl methacrylate, prevents crosslinking and yields soluble PE containing MAH units. Crosslinking, due to coupling of PE^˙ macroradicals formed by hydrogen abstraction from PE by excited MAH, is prevented by electron donation from the additive to the MAH⁺ cation which is present in the MAH+?MAH excimer as well as in the excimer which is appended to the PE.     

Investigation of drug release and 1H‐NMR analysis of the in situ forming systems based on poly(lactide‐co‐glycolide)

In situ forming biodegradable polymeric systems loaded with betamethasone (BTM) and betamethasone acetate (BTMA) were prepared using poly(DL ‐lactide‐co‐glycolide) (PLGA), ethyl heptanoate (EH), and N‐methyl‐2‐pyrrolidone (NMP) as the biodegradable polymer, additive, and solvent, respectively. The drug release studies were carried out in buffer (pH = 7.4, 37°C) using high performance liquid chromatography (HPLC). ¹H‐NMR was used to determine the polymer degradation behavior, release mechanism, and interactions between the polymer and drug. The ¹H‐NMR spectra showed that all interactions between the polymer and drug were hydrogen bonding. Hydroxyl groups and fluorine in drugs were involved in hydrogen bonding with PLGA polymer. In ¹H‐NMR studies, we found that the degradation rate in the systems loaded with BTMA was higher than the systems loaded with BTM because BTMA is only slightly soluble and accelerates the hydrolysis of PLGA chains. The formulations loaded with BTM had obviously lower burst release compared with BTMA loaded samples. With respect to ¹H‐NMR spectra, the mechanism of BTM release is controlled by two effective factors: solvent removal and polymer degradation. Copyright © 2008 John Wiley & Sons, Ltd.     

Structure study of the furan–maleic anhydride copolymer

A structural study of furan–maleic anhydride copolymer (F–MAH) was undertaken to confirm its alternating nature and to determine its microstructure. The spectral properties of a model compound representing the alternating repeat unit, 2-(2-tetrahydrofuranyl)succinic anhydride, were compared with those of F–MAH. Their infrared (IR), ¹H, and ¹³C nuclear magnetic resonance (NMR) spectra (after compensating for the absence of the olefinic double bond) were in good agreement with those of the copolymer. Furthermore, the observed splitting in the ¹H- and ¹³C-NMR spectra of F–MAH were assigned to cis–trans linkages on both the F and MAH units, with cis linkage being favored on both units, especially the former. The structure of 2,5-dimethylfuran (DMeF)–MAH copolymer is similar to that of F–MAH copolymer, except that the preference of cis linkages is less pronounced. The structure of 2-methylfuran (MF)–MAH copolymer is a complex structure with numerous 2,3-furandiyl units. A mechanistic study was undertaken to elucidate the roles of F–MAH Diels–Alder adduct, and the charge-transfer (CT) complex in the radical initiated copolymerization. The adduct reverted substantially to monomers under the reaction conditions; but, the amount of adduct remaining at equilibrium was quite appreciable; therefore, its participation could be ruled out on this basis alone. However, on polymerizing the adduct in the presence of F-d₄, the latter was incorporated into the copolymer to an extent indicative of free monomer exchange. Therefore, the adduct cannot be directly involved in the polymerization.     

Novel amine-containing biodegradable polyester via copolymerization of aspartic anhydride and 1,4-cyclohexanedimethanol

A novel biodegradable polyester having pendant amine functional groups was snythesized from N-(benzyloxycarbonyl)-L -aspartic anhydride ( 2 ) and 1,4-cyclohexanedimethanol ( 3 ) by polycondensation reaction using p-toluenesulfonic acid as a catalyst. The synthesized polymer 4 shows the characteristic ester carbonyl absorption peak at 1732 cm⁻¹ in the IR spectrum, and the NMR spectra were consistent with the IR data. Also, the elemental analysis showed that the experimental and calculated values were very close to each other. The weight-average molecular weight of the polymers ranged from 1140 to 5050 and increased with increasing reaction time. This new polymer would have the potential of a drug delivery biomaterial.     

Plasma surface modification of poly (l-lactic acid) and poly (lactic-co-glycolic acid) films for improvement of nerve cells adhesion

Radio frequency (RF) plasma treatment in O₂ was applied to modify the surface of poly (l-lactic acid) (PLLA) and poly (d,l-lactic acid-coglycolic acid) (PLGA) as biodegradable polymers. The surface structure, morphology, wettability and surface chemistry of treated films were characterized by water drop contact angle measurement, scanning electron microscope (SEM), optical invert microscope, differential scanning calorimetry (DSC) and ATIR–FTIR spectroscopy. The cell affinity of the oxygen plasma treated film was evaluated by nervous tissue B65 cell culture in stationary conditions. The results showed that the hydrophilicity increased greatly after O₂ plasma treatment. The results showed that improved cell adhesion was attributed to the combination of surface chemistry and surface wettability during plasma treatment. Cell culture results showed that B65 nervous cell attachment and growth on the plasma treated PLLA was much higher than an unmodified sample and PLGA. Surface hydrophilicity and chemical functional groups with high polar component play an important role in enhancing cell attachment and growth.     

Synthesis of dendronized polymer brushes containing metallo‐supramolecular polymer side chains

A new kind of dendronized polymer brush with metallo‐supramolecular polymer side chains was fabricated by a combination of macromonomer and graft‐to approach. The alternating copolymers of maleic anhydride and styryl macromonomers pendant with Fréchet‐type dendrons of three generations were reported previously. In this article, terpyridine groups were introduced along the backbone of the dendronized polymers through the amidolysis of anhydride groups. The terpyridine functionalized PEO linear chains were then incorporated through the complexation of terpyridine and Ru(II) ion. Thus, dendronized polymer brushes with amphiphilic properties were synthesized. AFM analysis showed worm‐like single molecular morphologies of the polymers of three generations, and ¹H NMR analysis indicated that such molecular brushes had an amphiphilic nature in solution. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3303–3310, 2007     

Solution properties of chlorinated polypropylene and maleic anhydride grafted chlorinated polypropylene

The solution behaviors of the chlorinated polypropylene (CPP) and its grafted polymers (CPP-g-MAH) were systematically studied to characterize their polar change with grafting maleic anhydride (MAH) onto the chain of CPP. The molecular weights of the polymers were determined with light scattering measurements, and the Mark–Houwink equation of CPP in toluene was also obtained. The result showed that the Mark–Houwink equation of CPP was suitable for estimating the molecular weight of the polydisperse samples of CPP and not suitable to CPP-g-MAH because the molecular polarity of the graft polymers had changed with grafting MAH onto CPP. The solubility result of CPP and CPP-g-MAH in various solvents indicated that the polarity of CPP gradually increased with grafting MAH onto its chain, which would cause the solubility of poorly hydrogen bonded solvents for CPP-g-MAH to gradually become poor, whereas that of moderately hydrogen bonded solvents for the polymers becomes better with an increase of the MAH graft content. This is consistent with the results of their dilution ratio and solubility parameter. Stabilities of the 344^# resin–CPP-g-MAH–toluene solutions showed that the miscibility of CPP-g-MAH and 344^# resin was improved with increase of the MAH grafted content.     

Copolymerization of furan with maleic anhydride initiated by thioglycolic acid

Copolymerization of furan (F) with maleic anhydride (MAH) initiated by thioglycolic acid (TGA) was studied in various solvents and temperatures in the presence of atmospheric oxygen. Copolymer between F and MAH was readily obtained by using thiol compounds as initiators. The atmospheric oxygen catalyses the copolymerization reaction. The rate of copolymerization is proportional to the concentration [TGA]^0.55 at low concentrations (< 1.0 mol/L), at higher concentrations rates decrease gradually. The copolymerization rate increases with increase in copolymerization temperature and varies with the total monomer concentration as ([F] + [MAH])^1.9. The overall energy of activation as calculated from the Arrhenius plot has been found to be 6.4 Kcal/mol within the temperature range of 25–50°C.     

Hygrothermal aging of Nafion

The membrane durability is a critical issue for the development of Proton Exchange Membrane Fuel Cells (PEMFC). Since PEMFC in situ tests were not conclusive to determine Nafion^® membrane degradation mechanism, ex situ aging tests were performed on Nafion^® 112 in practical fuel cell usage conditions. The polymer chemical structure evolution was investigated by infrared spectroscopy (IR) and Nuclear Magnetic Resonance (NMR) while its hydrophilicity, directly linked to its protonic conductivity, is established through sorption isotherms by Dynamical Vapour Sorption (DVS). Durability studies over a period of 400 days revealed membrane degradation through a modification of sulfonic acid end-groups. Formation of sulfonic anhydride (from the condensation of sulfonic acids) was strongly demonstrated by IR spectroscopy and, indirectly, by NMR. The substitution of ionic end-groups by less hydrophilic anhydrides leads to a significant decrease of water uptake and thus of its hydrophilicity. Surprisingly, kinetic study reveals that the hygrometric level accelerates this condensation reaction.     

Laminating resins obtained from 2,2′-(1,4-phenylenedivinylene)bispyridine bismaleimides and maleimide-terminated styrylpyridine prepolymers

A new bismaleimide (2a) , biscitraconimide (2b) , and bisnadimide (4) were synthesized by reacting 2-amino-6-methylpyridine with an equimolar amount of maleic, citraconic, or nadic anhydride, respectively, and then with a half molar amount of 1,4-benzenedicarbaldehyde in the presence of acetic anhydride. They, as well as the intermediate amic acids ( 1a, 1b, and 3 ) were characterized by IR and ¹H-NMR spectroscopy. The DTA thermograms showed that crosslinking of polymer precursors started at 180–212°C. The crosslinked resins obtained from 2a and 2b were stable up to 300–313°C and afforded anaerobic char yield of 53–60% at 800°C. The cured resin of 4 was less thermostable. In addition, end-capping of styrylpyridine prepolymers was accomplished by reacting 2,6-dimethylpyridine (n mol) with 1,4-benzenedicarbaldehyde (n + 1 mol) in acetic anhydride to yield a formyl-terminated styrylopyridine prepolymer. The latter reacted with the maleamic acid 1a (2 mol) to afford a series of maleimide-terminated styrylpyridine prepolymers MTSOs. They showed lower curing temperatures than did the ordinary poly(styrylpyridine). Their cured resins did not lose weight up to 310–344°C both in N₂ or air and afforded anaerobic char yield of 66-72% at 800°C.     

Chemically Modified Chitosan Beads as Molecularly Imprinted Polymer Matrix for Adsorptive Separation of Proteins

In a phosphate buffer, a hemoglobin (Hb)-imprinted polymer complex was preparedusing maleic anhydride (MAH) modified chitosan beads as matrix, acrylamide (AM) as functionalmonomer, N,N-methylenebisacrylamide (MBA) as cross-linker and potassiumpersulfate (KPS) /sodium hydrogen sulfite (NaHSO3) as initiators. Langmuir analysis showed that an equal class ofadsorption was formed in the molecular imprinting polymer (MIP), and the MIP has highadsorption capacity and selectivity for the imprinted molecule. The MIP can be reused and therecovery was approximately 100% at low concentration.