Lifetime prediction of biodegradable polymers

Exploring the Long-Term Hydrolytic Behavior of Zwitterionic Polymethacrylates and Polymethacrylamides

The hydrolytic stability of polymers to be used for coatings in aqueous environments, for example, to confer anti-fouling properties, is crucial. However, long-term exposure studies on such polymers are virtually missing. In this context, we synthesized a set of nine polymers that are typically used for low-fouling coatings, comprising the well-established poly(oligoethylene glycol methylether methacrylate), poly(3-(N-2-methacryloylethyl-N,N-dimethyl) ammoniopropanesulfonate) ("sulfobetaine methacrylate"), and poly(3-(N-3-methacryamidopropyl-N,N-dimethyl)ammoniopropanesulfonate) ("sulfobetaine methacrylamide") as well as a series of hitherto rarely studied polysulfabetaines, which had been suggested to be particularly hydrolysis-stable. Hydrolysis resistance upon extended storage in aqueous solution is followed by ¹H NMR at ambient temperature in various pH regimes. Whereas the monomers suffered slow (in PBS) to very fast hydrolysis (in 1 M NaOH), the polymers, including the polymethacrylates, proved to be highly stable. No degradation of the carboxyl ester or amide was observed after one year in PBS, 1 M HCl, or in sodium carbonate buffer of pH 10. This demonstrates their basic suitability for anti-fouling applications. Poly(sulfobetaine methacrylamide) proved even to be stable for one year in 1 M NaOH without any signs of degradation. The stability is ascribed to a steric shielding effect. The hemisulfate group in the polysulfabetaines, however, was found to be partially labile.

Advanced Materials by Atom Transfer Radical Polymerization

Atom transfer radical polymerization (ATRP) has been successfully employed for the preparation of various advanced materials with controlled architecture. New catalysts with strongly enhanced activity permit more environmentally benign ATRP procedures using ppm levels of catalyst. Precise control over polymer composition, topology, and incorporation of site specific functionality enables synthesis of well-defined gradient, block, comb copolymers, polymers with (hyper)branched structures including stars, densely grafted molecular brushes or networks, as well as inorganic-organic hybrid materials and bioconjugates. Examples of specific applications of functional materials include thermoplastic elastomers, nanostructured carbons, surfactants, dispersants, functionalized surfaces, and biorelated materials.

Chitosan/CaCO3-silane nanocomposites: Synthesis, characterization, in vitro bioactivity and Cu(II) adsorption properties

Chitosan nanocomposites containing 2, 5, 8wt% of calcium carbonate-γ-aminopropyl triethoxy silane (CS/CC-ATS NCs) were prepared by ultrasonic irradiation. After characterizing of physicochemical properties of the obtained CS/CC-ATS NCs, their performance was evaluated for both the bone-like apatite mineralization and the removal of Cu(II). The field emission-scanning electron microscopy images from the in vitro bioactivity of the CS and the CS/CC-ATS NC 5wt% displayed that the hydroxyapatite was produced on the samples surface. However, the distribution of it on the surface of CS/CC-ATS NC 5wt% was better than the pure CS. The uptake of Cu(II) on the CS/CC-ATS NC 5wt% was studied under different adsorption conditions such as contact time, the initial concentration of metal ion and adsorbent amount. The results of isothermal adsorption of the pure CS and the CS/CC-ATS NC 5wt% were well fitted by Langmuir model for Cu(II) with adsorption capacity of 33.33 and 33.90mg·g^-1, respectively. As a result, the CS/CC-ATS NC has great potencies in both the bone tissue engineering and the uptake of toxic metal from solution.

A Carbomethoxylated Polyvalerolactone from Malic Acid: Synthesis and Divergent Chemical Recycling

We report here the synthesis of a novel substituted polyvalerolactone from the renewable monomer, 4-carbomethoxyvalerolactone (CMVL, two steps from malic acid). The polymerization proceeds to high equilibrium monomer conversion to give the semicrystalline carbomethoxylated polyester with low dispersity. The material displays a glass transition temperature of -18 °C and two melting temperatures at 68 and 86 °C. This polymer can be chemically recycled by either of two independent pathways. The first (red) cleanly returns CMVL by a backbiting depolymerization from the hydroxy terminus; the second (blue) uses a base to cleave the polyester in a retro-oxa-Michael fashion. This affords a methacrylate-like monomer that we have polymerized radically to a new polymethacrylate analogue. This is a rare example of a polymer that has been shown to have two independent chemical recycling pathways leading to two different classes of monomers.

In Vitro Degradation Behaviors of Manganese-Calcium Phosphate Coatings on an Mg-Ca-Zn Alloy

In order to decrease the degradation rate of magnesium (Mg) alloys for the potential orthopedic applications, manganese-calcium phosphate coatings were prepared on an Mg-Ca-Zn alloy in calcium phosphating solutions with different addition of Mn2+. Influence of Mn content on degradation behaviors of phosphate coatings in the simulated body fluid was investigated to obtain the optimum coating. With the increasing Mn addition, the corrosion resistance of the manganese-calcium phosphate coatings was gradually improved. The optimum coating prepared in solution containing 0.05 mol/L Mn2+ had a uniform and compact microstructure and was composed of MnHPO4·3H2O, CaHPO4·2H2O, and Ca3(PO4)2. The electrochemical corrosion test in simulated body fluid revealed that polarization resistance of the optimum coating is 36273 Ωcm2, which is about 11 times higher than that of phosphate coating without Mn addition. The optimum coating also showed the most stable surface structure and lowest hydrogen release in the immersion test in simulated body fluid.

LDPE Oxidation by CO2 Laser Radiation (10.6 µm)

Thermooxidation of LDPE films by CO2 laser radiation, 10.6 μm, was characterized by Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR). The formation of carbonyl and hydroxyl functional groups onto LDPE films was dependent on the fluency of CO2 laser. IR absorption of vinyl groups and C-O bond present in alcohols showed a decrease and an increase, respectively, indicating that CO2 laser radiation causes simultaneous formation and accumulation of hydroperoxides in LDPE films; furthermore, crystallinity of LDPE films irradiated with CO2 tends to increase. So, CO2 laser radiation is able to oxidize the LDPE films, obtaining a PE with similar spectroscopic properties to that of PE-BIO by a physical process.

Pressure-controlled crystallization of stereocomplex crystals in enantiomeric polylactides with remarkably enhanced hydrolytic degradation

Enantiomeric biopolymers, with improved combinatorial heat resistance, hydrolytic degradation and hydrophilicity, were fabricated by pressure-controlled crystallization of stereocomplex crystals.

Photo-triggered enzymatic degradation of biodegradable polymers

Control over the initiation of enzymatic degradation of biodegradable polymers was demonstrated by tuning the solid-molten state of a surface coated azo-compound with light irradiation.