Simple One-Pot Synthesis of Fully Biobased Unsaturated Polyester Resins Based on Itaconic Acid

© 2017 American Chemical Society. For the preparation of fully biobased unsaturated polyester resins (UPRs), the replacement of styrene with alternate nonpetroleum-based monomers turned out to be one of the most challenging tasks. Its complexity lies in the fact that reactive diluents (RD) have to have low viscosity and volatility, good compatibility with prepolymer, and capability to homopolymerize and copolymerize with its unsaturations. In this context, we directed our efforts to develop fully biobased UPRs using the dialkyl itaconates as an alternative to styrene. Therefore, a series of 100% biobased UPRs were prepared from itaconic acid and 1,2-propandiol and diluted by dialkyl itaconates. The resins were characterized by Fourier transform infrared spectroscopy, NMR, volatility, and viscosity measurements, while the cured samples were characterized by dynamic mechanical properties, thermomechanical analysis, thermogravimetric analysis data, and tensile tests. The influence of RD structure on the properties of cured samples was discussed in detail. It was shown that the prepared resins had evaporation rates of dialkyl itaconates of several orders of magnitude less compared to styrene. The cured resins with dimethyl itaconate showed comparable or even better thermal and mechanical properties compared to the one with styrene. This investigation showed that itaconic acid and dialkyl itaconates are promising bioresources for the preparation of fully biobased UPRs for mass consumption

Hydrogels based on poly(methacrylic acid) and nanocellulose with potential application in dental treatments

pH sensitive hydrogels, such as hydrogels based on poly(methacrylic acid) (PMAA), are tremendous materials with great properties due to which they have application in many fields, such as: targeted drug delivery, tissue engineering, as contact lenses etc. Hydrogels based on PMAA are non-toxic, biocompatible and able to absorb and retain huge amount of water. These hydrogels are widely used for targeted drug delivery due to their specific pH swelling behavior which enable drug release in environments with pH values higher than pKa(PMAA). However, poor mechanical properties of hydrogels based on PMAA often limit their application. In order to overcome this limitation, green approach is used in present study. Namely, nanocellulose (NC) extracted from wood waste material is added to PMAA due to NC non-toxicity, biocompatibility, biodegradability and great mechanical properties (which is used for improvement of hydrogels mechanical characteristics). Further improvement of hydrogels based on PMAA and NC is achieved by adding carboxymethyl cellulose (CMC). CMC is non-toxic, biocompatible, biodegradable, pH-sensitive derivate of cellulose widely used in drug delivery systems. Drug delivery system prepared in that way can enable controlled release of drug (such as lidocaine hydrochloride (Lid)) for prolonged period of time and therefore, reduce the number of acquired drug dosages which further lead to safe and efficient drug application. Therefore, Lid is encapsulated in hydrogels based on PMAA, NC and CMC (PM/NC-Lid). Lid is local anesthetic often used in dental treatment and it is usually administrated by injection, which is painful, unpleasant and treatment is often required several dosages. These limitations can be overcome by applying PM/NC-Lid hydrogels as buccal patches for controlled release of lidocaine hydrochloride. Present study describes green synthesis and characterization of PM/NC-Lid hydrogels (using the Fourier Transform Infrared spectroscopy (FT-IR), the Scanning Electron Microscopy (SEM) and the single compression tests). Also, PM/NC-Lid swelling behavior and Lid controlled release from PM/NC-Lid hydrogels is investigated depending on the variable synthesis parameter (NC wt%) in simulated buccal environment. Results presented in this study show that PM/NC-Lid hydrogels are promising materials for controlled release of anesthetic drugs and for potential application as buccal patches in dental treatments

The Mechanical Properties of a Poly(methyl methacrylate) Denture Base Material Modified with Dimethyl Itaconate and Di-n-butyl Itaconate

This study investigates a wide range of clinically relevant mechanical properties of poly(methyl methacrylate) (PMMA) denture base materials modified with di-methyl itaconate (DMI) and di-n-butyl itaconate (DBI) in order to compare them to a commercial PMMA denture base material. The commercial denture base formulation was modified with DMI and DBI by replacing up to 10 wt% of methyl methacrylate (MMA) monomer. The specimens were prepared by standard bath curing process. The influence of the itaconate content on hardness, impact strength, tensile, and thermal and dynamic mechanical properties was investigated. It is found that the addition of di-n-alkyl itaconates gives homogenous blends that show decreased glass transition temperature, as well as decrease in storage modulus, ultimate tensile strength, and impact fracture resistance with increase in the itaconate content. The mean values of surface hardness show no significant change with the addition of itaconates. The magnitude of the measured values indicates that the poly(methyl methacrylate) (PMMA) denture base material modified with itaconates could be developed into a less toxic, more environmentally and patient friendly product than commercial pure PMMA denture base material

Optimization of Reactive Diluent for Bio-Based Unsaturated Polyester Resin: A Rheological and Thermomechanical Study

Nowadays, unsaturated polyester resins (UPR) are mainly obtained from non-renewable resources. The ever-increasing regulations and the continuous demand for more sustainability have led to extensive research towards more environmentally suitable alternatives to petroleum-based materials. However, one of the main disadvantages of bio-based UPR is their relatively high viscosity compared to petrochemical ones. In order to overcome this drawback, in this work, we investigated the possibility to lower the resin viscosity utilizing a mixture of dimethyl itaconate (DMI) and methyl methacrylate (MMA) as a reactive diluent. The effect of the DMI and MMA ratio on resin rheological properties was investigated. The optimal curing parameters were determined and all UPRs had a high gel content, which was shown to be dependent on the DMI and MMA ratio in the formulation. Furthermore, thermomechanical and mechanical properties of the resulting network were also found to be affected by the used reactive diluent mixture. A small substitution of DMI by MMA proved to be advantageous since it offers lower resin viscosity and improved mechanical properties

Mechanical properties of composites based on unsaturated polyester resins obtained by chemical recycling of poly(ethylene terephthalate)

Composites based on unsaturated polyester (UPe) resins and fumed silica AEROSIL® RY 50, NY 50, RX 50 and NAX 50, as well as graphite, TiO2 or organically modified clay CLOISITE 30B were prepared in order to investigate the influence of reinforcing agents on the mechanical properties of composites. Unsaturated polyester resins were synthesized from maleic anhydride and products of glycolysis, obtained by depolymerization of poly(ethylene terephthalate) with dipropylene glycol (UPe1 resin) and triethylene glycol (UPe2 resin) in the presence of tetrabutyl titanate catalyst. The obtained unsaturated polyesters were characterized by FTIR spectroscopy, acid and hydroxyl values, and their mechanical properties were also examined. Significant increase of the tensile modulus, tensile strength and decrease of the elongation at break was observed for composites prepared after addition of 10 wt.% of graphite or 10 wt.% of TiO2 to the UPe resins, indicating strong interaction between matrix and filler particles. On the other hand, nanocomposites prepared using UPe2 and hydrophobically modified silica nanoparticles showed lower tensile strength and tensile modulus than polymer matrix. The presence of CLOISITE 30B had no significant influence on the mechanical properties of UPe1, while tensile strength and tensile modulus of UPe2 increased after adding 10 wt.% of clay.U ovom radu sintetisani su kompoziti na bazi nezasićenih poliestarskih (UPe) smola i SiO2 (AEROSIL®:RY 50, NY 50, RX 50 i NAX 50), grafita, TiO2 ili organski modifikovane gline CLOISITE 30B u cilju ispitivanja uticaja punioca na mehanička svojstva kompozita. Nezasićene poliestarske smole su sintetisane polazeći od anhidrida maleinske kiseline i proizvoda glikolize dobijenih depolimerizacijom poli(etilen-tereftalata) sa dipropilen glikolom (UPe1 smola) ili trietilen glikolom (UPe2 smola) u prisustvu katalizatora tetrabutil titanata. Sintetisane nezasićene poliestarske smole su ispitane primenom FTIR spektroskopije, određen im je kiselinski i hidroksilni broj i ispitana su njihova mehanička svojstva. Molarna masa srednja po brojnoj vrednosti sintetisanih nezasićenih poliestarskih smola je između 1620-1630 g mol-1. Moduli istezanja i zatezna čvrstoća kompozita pripremljenih dodavanjem 10 mas.% grafita ili TiO2 nezasićenim poliestarskim smolama su značajno porasli u odnosu na čiste poliestre, dok se izduženje pri kidanju smanjilo, što ukazuje na postojanje jakih interakcija između matrice i čestica punioca. Sa druge strane, nanokompoziti sintetisani korišćenjem UPe2 i modifikovanih nanočestica SiO2 su imali manju zateznu čvrstoću i module istezanja nego čista nezasićena poliestarska smola. Pokazano je da prisustvo gline CLOISITE 30B nema značajan uticaj na mehanička svojstva smole UPe1, dok su vrednosti modula istezanja i zatezne čvrstoće UPe2 porasle nakon dodavanja 10 mas.% gline

The effects of wild-type and mutant SOD1 on smooth muscle contraction

In this work we compared the mutated liver copper zinc-containing superoxide dismutase (SOD1) protein G93A of the transgenic rat model of familial amyotrophic lateral sclerosis (FALS), to wild-type (WT) rat SOD1. We examined their enzymatic activities and effects on isometric contractions of uteri of healthy virgin rats. G93A SOD1 showed a slightly higher activity than WT SOD1 and, in contrast to WT SOD1, G93A SOD1 did not induce smooth muscle relaxation. This result indicates that effects on smooth muscles are not related to SOD1 enzyme activity and suggest that heterodimers of G93A SOD1 form an ion-conducting pore that diminishes the relaxatory effects of SOD1. We propose that this type of pathogenic feedback affects neurons in FALS

Effect of neutralization degree of methacrylic acid on hydrogel swelling and drug release

Drug delivery system is an amazing tool which is widely used for drug protection and its controlled release in order to enhance drug bioavailability, reduce side effects and therefore to improve overall therapy. Hydrogels have been attracted great attention as drug carriers due to their great physicochemical properties, similarity to the living tissues and biocompatibility. One group of pH sensitive hydrogels are based on poly(methacrylic acid) (PMAA). These non-toxic hydrogels are used as drug delivery system because they swell as a response to the change in pH of external environment and drug is being released during the process. In present study, in order to improve the control of drug release rate, caffeine was encapsulated in liposomes which were further embedded into PMC hydrogel (PMCL). It was investigated how the change in neutralization degree of methacrylic acid affect the swelling degree of PMCL hydrogels and caffeine release in two environments at 37 °C for 24 h: 0.1 M hydrochloride acid (pH 1) and phosphate buffer with pH value of 6.8 (pH 6.8), as a simulation of pH environment in human stomach and intestines, respectively. Obtained results show that PMCL hydrogels have great potential for controlled release of poorly water-soluble drugs in human intestines

Modification of hydrophilic polymer network to design a carrier for a poorly water-soluble substance

pH sensitive, nontoxic, and biocompatible poly(methacrylic) acid (PMAA) based soft networks have been extensively used in the design of systems for targeted drug delivery. Still, their highly hydrophilic nature limits their potential to be used as a carrier of poorly water-soluble substances. With the aim to overcome this limitation, the present study details a new approach for modification of PMAA based carriers using two amphiphilic components: casein and liposomes. The FTIR analysis revealed structural features of each component as well as the synergetic effect that originated from the formation of specific interactions. Namely, hydrophobic interactions between the poorly water-soluble model drug (caffeine) and casein enabled caffeine encapsulation and controlled release, while addition of liposomes ensured better control of the release rate. The morphological properties of the carriers, swelling behavior, and release kinetics of caffeine were investigated depending on the variable synthesis parameters (neutralization degree of methacrylic acid, concentration of caffeine, presence/absence of liposomes) in two different media simulating the pH environment of human intestines and stomach. The data obtained from in vitro caffeine release were correlated and analyzed in detail using several mathematical models, indicating significant potential of investigated carriers for targeted delivery and controlled release of poorly water-soluble substances

Methacrylic Acid Based Polymer Networks with a High Content of Unfunctionalized Nanosilica: Particle Distribution, Swelling, and Rheological Properties

The poor stability and tendency to agglomerate of unfunctionalized nano-SiO₂ in the presence of ionic species presents a challenge for preparing poly­(methacrylic acid)/nano-SiO₂ nanocomposite (NC) hydrogels with desired strength and swelling capability. We proposed a facile and eco-friendly method for the preparation of PMAA/SiO₂ NC hydrogels using unfunctionalized silica nanoparticles (NPs) in the form of a suspension. SEM and TEM analyses showed that the NP distribution in the polymer matrix highly depended on the particle concentration. At lower concentrations (up to 13.9 wt %), the NPs were uniformly dispersed as single nanoparticles. With an increase in NP concentration, homogeneously dispersed nanoscale aggregates were formed, while a further increase in the silica concentration led to the formation of homogeneous structures consisting of mutually interacting nanosilica particles coated with PMAA. Swelling experiments confirmed that the silica NPs behaved as adhesive fillers that interacted with PMAA chains, causing the formation of a thin polymer layer strongly adsorbed at the particle interface. The thicknesses of the adsorbed polymer layer, as well as the swelling kinetic parameters, were strongly influenced by nanoparticle size and concentration. Combining nanosilica and PMAA in the form of a soft hydrogel network provided stabilization of the NPs and ensured better mechanical properties of the obtained NC hydrogels compared to pure polymer matrix. The optimal loadings, necessary to ensure the most improved dynamical-mechanical properties, were found in the case of the formation of homogeneously dispersed, nanosized silica aggregates in a PMAA matrix

Recommendations for replacing PET on packaging, fiber, and film materials with biobased counterparts

This review sheds light on urgent questions that arise from the need to replace a polymer resin,-poly(ethylene terephthalate), which represents 7.7% market-share in the global plastic demand (Plastics-the Facts 2019), by renewable alternatives. The main question that this review will address is: what are the most promising PET replacements made from biomass? Currently, under debate is naturally its biobased counterpart bio-PET (or even recycle rPET), as well as other aromatic key-players with comparable thermo-mechanical performance and enhanced barrier properties, such as poly(ethylene 2,5-furandicarboxylate) (PEF) and poly(trimethylene 2,5-furandicarboxylate) (PTF). They are most adequate for packaging, but not restricted to. Additional alternatives are the miscellaneous of lignin-based thermoplastic polymers, although the technology involved in this latter case is still premature. (Bio)degradable aliphatic polyesters, despite their typical inferior thermo-mechanical properties, can also play a role e.g., among PET fiber industry applications. Poly(lactic acid) (PLA) is the most developed renewable polyester, already a commercial reality. All biobased polymers reviewed face a major hindrance for their wider deployment their cost-competitiveness. A pertinent question arises then: Are these alternatives, or will they be, economically feasible? Social, political and legal frameworks together with supportive financial schemes are boosting rapid changes. In the future, most probably more than one polymer will come to the market and will be used in some of the panoply of PET applications. This evaluation overviews sustainability issues, including perspectives on their green synthesis. Moreover, this review does also not neglect the accumulation of plastics waste in the environment and the inherent challenges of polymers' end-of-life. Approximately 8 M tons of polymers waste leaks into the environment each year, a fact not disconnected to PET's non-biodegradability and still insufficient collection and recycling rates. This journal i