Characterization of Chlorhexidine-Impregnated Cellulose-Based Hydrogel Films Intended for the Treatment of Periodontitis

Periodontitis comprises a chronic inflammation that is initiated by microbiota biofilm. If left untreated, periodontitis may lead to permanent tooth loss. Herein, we propose to design and improve a localized form of therapy comprising a chlorhexidine-impregnated hydrogel. Hydrogel films were prepared by varying the ratio between cellulose (MCC) and carboxymethylcellulose sodium (CMC) using the crosslinker epichlorohydrin (ECH). The hydrogel was loaded with chlorhexidine. Increasing the CMC ratio led to a reduction in the number of pores, an increase in their size, lower glass transition temperature ( T g ), decreased Young’s modulus, and increased film stretching and affected the time of release. Bacterial and fungal zones of inhibition showed similar activity and were not affected by the CMC and MCC ratio. Hydrogels loaded with chlorhexidine prevented the growth of S. oralis and C. albicans microorganisms and may provide a promising local delivery system for treating periodontitis.

Modifying chitosan with n-butyl acrylate - antibacterial ability

Polymer deriving from nature as Chitosan, which is one of the most abundant natural polymers in the world has effectively antibacterial potentiality. However, chitosan is relatively difficult for applications due to its disadvantageous properties. In this article, modifying chitosan (CS) is the grafting copolymerization using monomer n-butyl acrylate (BA) and tert-butyl hydroperoxide (TBHP) as an initiator. This process purposes to attain product having lower glass transition temperature (Tg) than original chitosan causing a wide range of applications but still keeping the capability of being an excellently antibacterial agent. The effects of parameters on synthesizing copolymer were studied by determining the grafting percentage (G%) and grafting efficiency (E%). The results revealed that the highest G = 242% and E = 61% were obtained at the conditions as following: BA/CS = 4 w/w, TBHP/CS = 5 v/w with [TBHP] = 20mM, [CS] = 0.75% w/v in acetic acid 0.6% and reaction temperature 90°C in 6 hours.

A New Strategy for the Synthesis of Hydroxyl Terminated Polystyrene-b-Polybutadiene-b-Polystyrene Triblock Copolymer with High Cis-1, 4 Content

This work reports the preparation of a hydroxyl terminated polystyrene-b-polybutadiene-b-polystyrene triblock copolymer (SBS) with high cis-1, 4 content via a novel nickel catalyst, [η3-Ni(CH2CHCHCH2OOCH3)][BPhF4]. FT-IR, 1H-NMR, and 13C NMR indicated that the polybutadiene segment of the copolymer contains greater than 90% cis-1, 4 structure, indicating achievement of the objective. Toward the functionalization goal, a hydroxyl group was successfully introduced at the end of the triblock copolymer (HO–SBS–OH). The results of gel permeation chromatography (GPC) revealed that the polymer is indeed a triblock copolymer, with no traces of homopolymer. Differential scanning calorimetry (DSC) showed that HO–SBS–OH synthesized using the novel catalyst had a lower glass transition temperature (Tg) than HO–SBS–OH synthesized with an alkyl lithium catalyst. Therefore, the polymer synthesized via the novel catalyst contains high cis-1,4 content and displays excellent low-temperature mechanical properties.

Direct cryopreservation of adherent cells on an elastic nanofiber sheet featuring a low glass-transition temperature

Electrospun nanofibers, featured a lower glass-transition temperature than the freezing temperature and a loose mesh structure, allows the direct cryopreservation of adherent cells towards the investigation of cell-material composites.

Synthesis and characterization of polyurethanes bearing carbosilane segments

New polyurethanes bearing carbosilane segment (1a–c) were synthesized and found to exhibit lower glass transition temperature and storage moduli than corresponding reference polyurethanes 2a–c, while thermal stability was retained.

Purification and characterization of kraft lignin

To upgrade the utilization of kraft lignin (KL) for high-performance lignin-based materials (e.g., carbon fiber), the purity, molecular mass distribution (MMD), and thermal properties need to be improved and adjusted to target values. Therefore, different methods, such as ultrasonic extraction (UE), solvent extraction, dialysis, and hot water treatment (HWT), were applied for the purification of KL. The chemical and thermal properties of purified lignin have been characterized by nuclear magnetic resonance, Fourier transform infrared, gel permeation chromatography, elemental analysis, differential scanning calorimetry, and thermogravimetric analysis. The lignin fractions obtained by UE with ethanol/acetone (E/A) mixture (9:1) revealed a very narrow MMD and were nearly free of inorganic compounds and carbohydrates. Further, the E/A-extracted lignin showed a lower glass transition temperature (Tg) and a clearly detectable melting temperature (Tm). Dialysis followed by HWT at 220°C is an efficient method for the removal of inorganics and carbohydrates; however, lignin was partly forming condensed structures during the treatment.

Synthesis and Characterization of Carboxyl-Terminated Hyperbranched Polyester

In order to prepare carboxyl-terminated hyperbranched polyester (HBP-COOH), succinic anhydride was used to modify hydroxyl-terminated hyperbranched polyester (HBP-OH), and the influences of the solvents, catalysts and time on the product’s structure were investigated. When THF is used as the solvent, sodium acetate as the catalyst, the molar ratio of succinic anhydride and hydroxyl groups is 3:1, and the reaction time is 6 h at 65°C, the modification extent of the hydroxyl groups is about 99% with about 95% yield. HBP-COOH has much lower glass transition temperature than that of HBP-OH due to its long and flexible end-groups.

Mechanical and Thermal Properties Biodegradable Microcellular Foams Based on Polylactide and Polycaprolactone

In this work, the producing of a series of biodegradable polylactide (PLA)/polycaprolactone (PCL) microcellular foams by rapid solvent casting method was investigated and discussed. Scanning electron microscopy (SEM) showed the average pore size in the structure was around 7 μm and the final microstructure was a combination of open and closed cells. The effect of PCL segments added on the mechanical and thermal behaviors was studied. According to the results, PLA/PCL biomaterial had lower glass transition temperature (Tg) in comparison with neat PLA polymer. In addition, the tensile strength and elastic modulus became poor when PCL added in. For obtained better mechanical and thermal properties, EC-blocked polyisocyanate (EC-bp), which was synthesized from reaction of toluene 2, 4-diisocyanate with dimethylol propionic acid and trimethylolpropane followed by addition of ethyl cellosolve (EC), were introduced. It was found that the tensile strength and elastic modulus were significantly increased by addition of EC-bp, which can be explained by coupling effect occurred between PLA and PCL.

Synthesis of aromatic polyimide bearing long alkyl chains through click reaction

A click reaction of aromatic polyimide having azide groups at both chainends (2), which was obtained by an azidation of polyimide having chloromethyl groups (1), was conducted with 1-octyne, leading to the polyimide having n-hexyl groups (3). 1H NMR spectroscopic analysis for 3 reveals that the n-hexyl groups were successfully introduced into the both chain-ends of aromatic polyimide and that a number-averaged molecular weight of the resulting polymer 3 was 6000. Differential scanning calorimetry analysis for 3 exhibited 30 °C lower glass transition temperature compared to that of 1, by introducing long alkyl groups into the aromatic polyimide chain.

Microporous Bio-Membrane Materials Based on High Molecular Weight Polylactide and Low Molecular Weight Poly(ethylene glycol)

In this work, microporous membrane biomaterials based on high weight molecular polylactide (PLA) and low molecular weight poly(ethylene glycol) (PEG) using rapid solvent evaporation method were prepared and investigated. The effect of PEG segments added on the thermal and degradation behaviors was studied. According to the results, produced PLA/PEG biomaterial has lower glass transition temperature (Tg)in comparison with neat PLA. It was also found that the degradation rates of the PLA/PEG biomaterials were significantly increased with adding of PEG, which explained by increasing hydrophilic groups. For better porous fixation, CL-blocked polyisocyanate (CL-bp), which was synthesized from reaction of isophorone diisocyanate (IPDI) with dimethylol propionic acid (DMPA) and Trimethylolpropane (TMP) followed by addition of caprolactam (CL), were introduced. The microporous forms were observed by the scanning electron microscope (SEM), which showed the mean diameters of prepared PLA/PEG microporous were around 10μm.