The copolymer poly(D,L-lactide-co-glycolide) is one of the most interesting polymers for medical applications. This interest is justified by the fact that it is bioreabsorbable, biocompatible and non-toxic, while its degradation kinetics can be modified by the copolymerization ratio of the monomers. In this study, copolymers were synthesised at 175?C by opening the rings of the cyclic dimers of the D,L-lactide and glycolide monomers in the presence of stannous octoate initiator and lauryl alcohol co-initiator. The application of vacuum to the reaction medium, coupled with adequate stirring, is essential for obtaining good results. The following analytical techniques were used to characterise the synthesised copolymers: Differential Scanning Calorimetry (DSC), Thermogravimetry (TG), Nuclear Magnetic Resonance Spectroscopy (NMR) and Fourier Transform Infrared Spectroscopy (FTIR). Both the input monomers and the reaction products were analysed. Important characteristics, such as melting temperature, glass transition temperature, thermal stability, chemical composition and the ratio of the monomers in the synthesised copolymer, were obtained from these analyses. These results helped to infer the absence of residual monomers in the synthesised copolymers
degradação que pode ser modificada pela razão entre os monômeros na copolimerização justifica tal interesse. Neste trabalho, os copolímeros foram sintetizados a 175 °C, por meio da abertura dos anéis dos dímeros cíclicos dos monômeros D,L-lactídeo e glicolídeo, na presença do iniciador octanoato de estanho e do co-iniciador álcool laurílico. O controle eficiente do vácuo no meio reacional, aliado à adequada agitação, foram fundamentais para o sucesso da síntese. Para caracterização dos copolímeros sintetizados foram empregadas as técnicas de calorimetria exploratória diferencial (DSC), termogravimetria (TG) e espectroscopia na região do infravermelho (FTIR). Foram analisados não somente os produtos de reação, mas também os monômeros de partida. A nova rota de síntese utilizada mostrou-se adequada, sendo os copolímeros poli(D,L-lactídeo-coglicolídeo) obtidos com sucesso. Palavras-chave: PLGA, poli (D,L-lactídeo-co-glicolídeo), biopolímero, síntese, caracterização, DSC, TG, FTIR. Synthesis and Thermal and Chemical Characterization of the Poly(D,L-lactide-co-glycolide) CopolymerAbstract: Poly (D, L-lactide-co-glycolide) copolymer (PLGA) has attracted a great deal of interest due to their special characteristics as biomaterials since it is bioreabsorbable, biocompatible, nontoxic and the kinetics of degradation can be modified by the ratio of monomers in copolymerization. In this work, the copolymers were synthesized at 175 °C, by opening the ring of cyclic dimers of D,L-lactide and glycolide monomers in the presence of tin(II) octanoate initiator and lauryl alcohol co-initiator. The efficient control of the vacuum in the medium combined with adequate stirring were essential to the success of the synthesis. Characterization of the copolymers samples was carried out by using differential scanning calorimetry (DSC), thermogravimetry (TG) and Fourier transform infrared spectroscopy (FTIR). We analyzed not only the products of reaction but also the initial monomers. The new synthesis route employed was appropriate and the poly(D, L-lactide-co-glycolide) was successfully obtained.
In the present work, rheological properties of HDPE samples were measured at temperatures of 150˚C, 190˚C and 230˚C. It was shown, by oscillatory tests, at low frequencies, that, for temperatures of 150˚C and 190˚C, there was a predominance of the viscous behavior over the elastic one. At 230˚C, there was a predominance of the elastic contribution, and there was an increase of the molar mass compared with the ones obtained from the tests at 150˚C and 190˚C. The results obtained from the temperature ramp oscillatory test showed that, up to around 248°C, the viscous behavior prevailed, the opposite being observed at higher temperatures. At 230˚C the sample showed significantly lower values of strain when compared with the ones observed at 150˚C and 190˚C. Oxidative induction time (OIT), melting point and degree of crystallinity were determined by differential scanning calorimetry (DSC). The DSC results and the rheological measurements showed a completely different behavior for the HDPE samples at 230˚C compared with the 150˚C and the 190˚C ones, suggesting that HDPE, at the temperature of 230˚C, underwent thermo-oxidative degradation with the initial predominance of crosslinking.
ResumoPolímeros Molecularmente Impressos (MIPs) são polímeros sintéticos que apresentam alta seletividade a uma molécula de interesse. O objetivo deste trabalho foi a síntese e caracterização de MIPs para aplicação na extração em fase sólida (SPE), visando a determinação de fenilalanina. Os MIPs foram sintetizados a partir do MAA, fenilalanina, EGDMA, AIBN, em clorofórmio. Também foi sintetizado o polímero não-impresso (NIP), para controle da seletividade dos MIPs. A dessorção da fenilalanina foi realizada em extrator Soxhlet. Os MIPs e NIP foram caracterizados pelas técnicas de análise: FTIR, UV-Vis, MEV, DSC e TG. O MIP apresentou maior capacidade adsortiva à fenilalanina do que o NIP, com uma taxa média de adsorção de 55% comparada a 11% para o NIP. Por MEV o MIP apresentou superfície mais porosa, importante característica para aplicação em SPE. Os estudos realizados mostraram que o MIP sintetizado apresentou grande potencial para aplicação em técnica de SPE. Palavras-chave: síntese e caracterização, MIP, fenilalanina, extração em fase sólida. AbstractMolecularly imprinted polymers (MIPs) are synthetic polymers that have high selectivity to a molecule of interest. The objective of this work was the synthesis and characterization of MIPs for use in solid phase extraction (SPE), in order to determine Phenylalanine. The MIPs were synthesized from the MAA, Phenylalanine, EGDMA AIBN, in chloroform. Non imprinted polymer (NIP) was synthesized to control the selectivity of MIPs. The desorption of Phenylalanine was carried out in Soxhlet extractor. The MIPs and NIP were characterized by the following analytical techniques: FTIR, UV-Vis, SEM, DSC and TG. MIP showed higher adsorption capacity to Phenylalanine than the NIP with an average rate of adsorption of 55% compared to 11% for NIP. SEM MIP showed more porous surface, an important feature for use in SPE. The synthesized MIP in the present study showed great potential for use in SPE technique.
High density polyethylene (HDPE) samples, containing different concentrations of prodegradant additive d2w ® , were prepared. The properties of the samples were evaluated through differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), rheometry, and scanning electron microscopy (SEM). The work contributes to decreasing the products made of non-biodegradable polymeric materials derived from fossil sources which are have become a problem due to their increasingly inappropriate disposal and long degradation time in the environment. The obtained results indicated that there was no degradation of the samples due to processing. No significant changes in melting temperature, crystallinity, viscoelastic behavior, molecular weight and chemical composition were observed. Images from SEM analysis showed particles on HDPE surface, attributed to prodegradant additive d2w ® . Oxidation Onset Temperature (OOT) results showed that the additive d2w® accelerated the degradation of HDPE. The activation energy (Ea) was determined by Ozawa-Wall-Flynn method. The obtained values were used for lifetime estimation of the samples. At 25˚C, HDPE with d2w ® showed a lifetime 50% higher than that of HDPE without this additive. This fact is attributed to the presence of stabilizers in masterbatch d2w ® and the absence of oxygen in thermogravimetric analysis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.