Methacrylate‐terminated polyisobutylenes (PIB‐MAs) were synthesized by transesterification of vinyl methacrylate by hydroxyl‐terminated polyisobutylenes (PIB‐OH) using Candida antarctica lipase B (Novozyme 435) catalyst in hexane at 50 °C. PIB CH2 CH2 CH2 OH and Glissopal OH, synthesized by anti‐Markovnikov hydrobromination of allyl‐terminated PIB and Glissopal®2300 followed by hydrolysis, were quantitatively converted into the corresponding PIB‐MAs. 1H and 13C NMR spectroscopy verified the formation of the expected structures. This “green” chemistry is a very promising methodology for polymer functionalization in general, and biomaterial synthesis in particular.
Research on novel implantable rubbery polyisobutylene‐based biomaterials carried out at the University of Akron during the past ∼15 years is outlined. Specific attention is paid to recent investigations focusing on the synthesis of semipermeable amphiphilic networks designed to be used as immunoisolatory membranes. The membranes envelop insulin‐producing living pig beta cells. They are biocompatible to the host (human) and the guest (beta cells) and remain permeable for many months in vivo. They are rubbery slippery, robust, sterilizable, optically transparent, with controlled pore dimensions that allow the in‐diffusion of glucose and nutrients, out‐diffusion of insulin and wastes, but they do not allow the entry of immunoproteins (IgG). The pores remain permeable for many months in vivo. The membranes are made by copolymerizig/crosslinking hydrophilic (meth)acrylates with methacrylate‐telechelic polyisobutylenes. Controlling the molecular weights of the constituent segments controls the pore sizes of the membranes. Immunoisolated pig beta cells enveloped in our membranes and implanted subcutaneously in a rat have corrected severe hyperglycemia. 相似文献
New linear and three-arm star polyisobutylenes carrying two and three terminal styryl endgroups, i.e., Fn = 2.0 and 3.0, respectively, have been prepared. The synthesis of these styryl-telechelic polyisobutylenes involved Friedel-Crafts alkylation by linear and/or three-arm star polyisobutylenes carrying tertiary chlorine endgroups of (2-bromoethyl)benzene or /β-bromoisopropylbenzene followed by de-hydrobromination. According to model studies, 1H-NMR, and UV spectroscopy, the conversions are essentially quantitative. These new terminally di- and tri-styrenated polyisobutylenes may be useful for the preparation of block copolymers and as cross-linking materials. 相似文献
Williamson type ether reactions were utilized for a high yield reaction of 4′‐chloro‐2,2′:6′,2″‐terpyridine with α,ω‐dihydroxy‐functionalized poly(ethylene oxide) and poly(oxytetramethylene)s to obtain bis(terpyridine)‐terminated telechelics. The completeness of the functionalization was proven by NMR spectroscopy, GPC and MALDI‐TOF‐MS investigations. The addition of transition metal ions resulted in a polyaddition polymerization leading to the formation of extended metallo‐supramolecular polymers, as proven by UV/VIS spectroscopy titration experiments. 相似文献
A chromophore terminated aliphatic polyether was obtained by polymer analogous conversion of the amino groups of Jeffamine® ED‐600 with 4‐[5‐(4‐acetoxy‐phenyl)‐3‐oxo‐penta‐1,4‐dienyl]benzoic acid and subsequent saponification of the acetoxy group. UV/Vis spectroscopic investigations showed that deprotonation of the chromophoric groups by organic or inorganic bases as for example poly(1,8‐octamethyleneacetamidine) and NaOH, respectively, results in a distinct bathochromic shift of the chromophores longest wavelength absorption band by about 100 nm. This effect is discussed in terms of polymer blends where the covalently bound chromophore can act as optical probe for acid–base interactions between the components.
A pyrene‐containing phenylboronic acid (PBA) functionalized low‐molecular‐weight hydrogelator was synthesized with the aim to develop glucose‐sensitive insulin release. The gelator showed the solvent imbibing ability in aqueous buffer solutions of pH values, ranging from 8–12, whereas the sodium salt of the gelator formed a hydrogel at physiological pH 7.4 with a minimum gelation concentration (MGC) of 5 mg mL?1. The aggregation behavior of this thermoreversible hydrogel was studied by using microscopic and spectroscopic techniques, including transmission electron microscopy, FTIR, UV/Vis, luminescence, and CD spectroscopy. These investigations revealed that hydrogen bonding, π–π stacking, and van der Waals interactions are the key factors for the self‐assembled gelation. The diol‐sensitive PBA part and the pyrene unit in the gelator were judiciously used in fluorimetric sensing of minute amounts of glucose at physiological pH. The morphological change of the gel due to addition of glucose was investigated by scanning electron microscopy, which denoted the glucose‐responsive swelling of the hydrogel. A rheological study indicated the loss of the rigidity of the native gel in the presence of glucose. Hence, the glucose‐induced swelling of the hydrogel was exploited in the controlled release of insulin from the hydrogel. The insulin‐loaded hydrogel showed thixotropic self‐recovery property, which hoisted it as an injectable soft composite. Encouragingly, the gelator was found to be compatible with HeLa cells. 相似文献
A mixed‐valence cluster of cobalt(II) hexacyanoferrate and fullerene C60‐enzyme‐based electrochemical glucose sensor was developed. A water insoluble fullerene C60‐glucose oxidase (C60‐GOD) was prepared and applied as an immobilized enzyme on a glassy carbon electrode with cobalt(II) hexacyanoferrate for analysis of glucose. The glucose in 0.1 M KCl/phosphate buffer solution at pH = 6 was measured with an applied electrode potential at 0.0 mV (vs Ag/AgCl reference electrode). The C60‐GOD‐based electrochemical glucose sensor exhibited efficient electro‐catalytic activity toward the liberated hydrogen peroxide and allowed cathodic detection of glucose. The C60‐GOD electrochemical glucose sensor also showed quite good selectivity to glucose with no interference from easily oxidizable biospecies, e.g. uric acid, ascorbic acid, cysteine, tyrosine, acetaminophen and galactose. The current of H2O2 reduced by cobalt(II) hexacyanoferrate was found to be proportional to the concentration of glucose in aqueous solutions. The immobilized C60‐GOD enzyme‐based glucose sensor exhibited a good linear response up to 8 mM glucose with a sensitivity of 5.60 × 102 nA/mM and a quite short response time of 5 sec. The C60‐GOD‐based glucose sensor also showed a good sensitivity with a detection limit of 1.6 × 10‐6 M and a high reproducibility with a relative standard deviation (RSD) of 4.26%. Effects of pH and temperature on the responses of the immobilized C60‐GOD/cobalt(II) hexacyanoferrate‐based electrochemical glucose sensor were also studied and discussed. 相似文献
We designed a novel water soluble topological structure polymer‐ferrocene‐ terminated hyperbranched polyurethane (HPU‐Fc) with good water solubility. The redox behaviors and the electrochemical kinetics parameters of HPU‐Fcs were explored by cyclic voltammetry (CV) according to electrochemical principle. The topological structure polymer was applied for the design and engineering of non‐enzymatic glucose sensor. The designed sensor showed good response to glucose concentration with good stability, favorable accuracy and high selectivity. The electrode was also used to detect glucose in blood samples, and the glucose contents detected by the electrode were in good agreement with those from the hospital where a common automatic biochemical analyzer (HF240–300) was used. This finding makes HPU‐Fc a promising biosensor for directly sensing glucose. 相似文献
POSS‐functionalized polyisobutylenes (PIBs) were synthesized by carbocationic polymerization using an epoxy‐POSS/TiCl4 initiating system in hexane/methyl chloride (60:40 v/v) solvent mixture at −80 °C. 1H NMR spectroscopy verified the incorporation of one epoxy‐POSS per polymer chain. Light scattering and TEM analysis demonstrated the formation of 50–100 nm sized aggregates and micron‐sized clusters.
Proton n.m.r. signals for two types of olefinic end groups, -CH2C(CH3)?CH2 (δ4.68 and δ4.87) and -CH?C(CH3)2 (δ5.21), have been observed in high molecular weight polyisobutylenes. Comparable amounts of both these end groups exist in commercial and laboratory prepared samples of polyisobutylenes contrary to previous reports that the former group is by far predominant. That different catalysts produce different relative concentrations of these end groups is demonstrated. Evidence for the presence of a third type of unsaturation from the -CH2C(CH2)?CH2- structure is discussed. 相似文献