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1.
Chempluschem ; 86(12): 1570-1576, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34851049

RESUMO

This work reports a simple and scalable strategy to prepare a series of thermoresponsive polyurethanes synthesized via copolymerization of dicyclohexyl diisocyanate with glycerol ethoxylate in a single one-pot system. These polyurethanes exhibit lower critical solution temperatures (LCST) at 57 °C. The LCST of synthesized polyurethane was determined from Dynamic Scanning Calorimetry and UV-vis measurements. Both the LCST and Tg of synthesized polyurethane was tuned by varying the ratio between hard segment (dicyclohexyl diisocyanate) and soft segment (glycerol ethoxylate). Thus, Tg values could be tuned from -54.6 °C to -19.9 °C for samples with different flexibility. The swelling and deswelling studies were done at room temperature and above the LCST respectively. The results showed that the swelling ratio increases with the increase of soft segment (glycerol ethoxylate) in synthesized polyurethanes. Furthermore, the mechanical properties of the membrane were studied by universal tensile testing measurements. Specifically, stress at break values varied from 0.35±0.07 MPa to 0.91±0.15 MPa for the tested membranes, whereas elongation at break data ranged from 101.9±20.9 % to 192.4±24.4 %, and Young's modulus varied from 0.35±0.03 MPa to 1.85±0.19 MPa. Tensile strength of the films increased with the increase of the hard segment and elongation at break decreased.

2.
Chem Commun (Camb) ; 57(63): 7762-7765, 2021 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-34250985

RESUMO

A novel methacrylate-based cross-linked polymer gel bearing an iridium photocatalyst showed air tolerance and pumping recyclability features through its tunable swelling and deswelling ability. The photocatalytic activity of the polymer gel was demonstrated through an E-to-Z isomerisation reaction and in an azide-alkene [2+3] cycloaddition.

3.
Macromol Rapid Commun ; 42(13): e2100213, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34031940

RESUMO

A new methodology for the pH-triggered degradation of polymers or for the release of drugs under visible light irradiation based on the cyclization of ortho-hydroxy-cinnamates (oHC) to coumarins is described. The key oHC structural motif can be readily incorporated into the rational design of novel photocleavable polymers via click chemistry. This main-chain moiety undergoes a fast photocleavage when irradiated with 455 nm light provided that a suitable base is added. A series of polyethylene glycol-alt-ortho-hydroxy cinnamate (polyethylene glycol (PEG)n -alt-oHC)-based polymers are synthesized and the time-dependent visible-light initiated cleavage of the photoactive monomer and polymer is investigated in solution by a variety of spectroscopic and chromatographic techniques. The photo-degradation behavior of the water-soluble poly(PEG2000 -alt-oHC) is investigated within a broad pH range (pH = 2.1-11.8), demonstrating fast degradation at pH 11.8, while the stability of the polymer is greatly enhanced at pH 2.1. Moreover, the neat polymer shows long-term stability under daylight conditions, thus allowing its storage without special precautions. In addition, two water-soluble PEG-based drug-carrier molecules (mPEG2000 -oHC-benzhydrol/phenol) are synthesized and used for drug delivery studies, monitoring the process by UV-vis spectroscopy in an ON/OFF intermittent manner.


Assuntos
Cinamatos , Polímeros , Sistemas de Liberação de Medicamentos , Concentração de Íons de Hidrogênio , Isomerismo , Polietilenoglicóis
4.
J Chromatogr A ; 1619: 460910, 2020 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-32008827

RESUMO

A pH-sensitive polymer based on the poly(styrene-alt-maleic anhydride) co-polymer serves as basis to develop a microextraction method (pH-HGME) in direct combination with high-performance liquid chromatography (HPLC) and fluorescence detection (FD) for the determination of seven organic compounds, including three polycyclic aromatic hydrocarbons (PAHs), three monohydroxylated PAHs and one alkylphenol, in urine. The method bases on the structural modification of the pH-sensitive polymer in the aqueous sample at a high pH value, followed by the formation and insolubilization of a hydrogel containing the preconcentrated analytes by decreasing the pH, and the direct injection of the hydrogel-rich phase in the HPLC-FD system. The optimization of the main variables permitted the selection of low amounts of aqueous sample (10 mL), which was mixed with 10 mg of co-polymer also present in a low volume (150 µL) of concentrated NaOH. The method further requires the addition of 200 µL of concentrated HCl, 3 min of stirring, and 15 min of centrifugation. This pH-HGME-HPLC-FD method presented low limits of detection, ranging from 0.001 µg L-1 to 0.09 µg L-1 in ultrapure water, average relative recoveries of 96.9% for the concentration level of 0.60 µg L-1, and enrichment factors between 1.50 and 17.7. The proposed method also exhibited high precision, with intermediate relative standard deviations lower than 16% for a concentration level of 0.60 µg L-1. The developed pH-HGME-HPLC-FD method performed adequately when analyzing two human urine samples provided by a non-smoker male and a smoker female, respectively. One of the target analytes (2-hydroxynaphthalene) was quantified in both samples using the standard addition method, with a predicted concentration of 7.3 ± 0.4 µg L-1 in the non-smoker male urine and 19.3 ± 0.6 µg L-1 in the smoker female urine.


Assuntos
Cromatografia Líquida de Alta Pressão , Microextração em Fase Líquida/métodos , Maleatos/química , Hidrocarbonetos Policíclicos Aromáticos/urina , Poliestirenos/química , Feminino , Fluorescência , Humanos , Concentração de Íons de Hidrogênio , Masculino , Fenóis/urina , Hidrocarbonetos Policíclicos Aromáticos/isolamento & purificação
5.
Soft Matter ; 15(38): 7695-7703, 2019 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-31502620

RESUMO

In spite of p-doped conducting polymers having been widely studied in the last decades and many applications having been developed, studies based on n-doped conducting polymers are extremely scarce. This fact is even more evident when it comes to conducting polymers n-doped with polycations, even though polyanions, such as poly(styrenesulfonate), are often used to obtain p-doped conducting polymers. In this work poly(pyridinium-1,4-diyliminocarbonyl-1,4-phenylene-methylene chloride), abbreviated as P(Py-1,4-P), has been used to prepare n-doped poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes by applying a reduction potential to a de-doped PEDOT film in a P(Py-1,4-P) water solution. The utilization of this cationic polyelectrolyte as an n-dopant agent results in drastic superficial changes, as is observed by comparing the morphology, topography and wettability of p-doped, de-doped and n-doped PEDOT. Cytotoxicity, cell adhesion and cell proliferation assays, which have been conducted using epithelial and fibroblast cell lines, show that the amount of P(Py-1,4-P) in the re-doped PEDOT films is below that required to observe a cytotoxic harmful response and that n-doped PEDOT:P(Py-1,4-P) films are biocompatible. The non-specific bacteriostatic properties of n-doped PEDOT:P(Py-1,4-P) films have been demonstrated against E. coli and S. aureus bacteria (Gram-negative and Gram-positive, respectively) using bacterial growth curves and adhesion assays. Although the bacteriostatic effect is in part due to the conducting polymer, as is proved by results for p-doped and de-doped PEDOT, the incorporation of P(Py-1,4-P) through the re-doping process greatly enhances this antimicrobial behaviour. Thus, only a small concentration of this cationic polyelectrolyte (∼0.1 mM) is needed to inhibit bacterial growth.

6.
Sci Rep ; 9(1): 7269, 2019 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-31086230

RESUMO

Detection of nitroaromatic explosives with high sensitivity and selectivity is extremely important for civilian and military safety. Here, we report the synthesis and multimodal sensing applications of an emissive alanine based dansyl tagged copolymer P(MMA-co-Dansyl-Ala-HEMA) (DCP), synthesized by RAFT copolymerization. The fluorescent co-polymer exhibited high sensitivity and selectivity towards conventional nitroaromatic explosives such as DNT, TNT and TNP in solution at lower range of µM level and also with saturated vapor of NACs. The quantum yield of the co-polymer was measured to be very high (Φf = 77%) which make it an ideal candidate for sensing in solution as well as in vapor phase. The fluorescence signal from DCP copolymer gets significantly quenched upon addition of aliquots of DNT, TNT, and TNP. The Stern-Volmer constant was calculated to be very high. The quenching mechanism was further established by fluorescence up-conversion, time-resolved fluorescence and steady state absorption spectroscopy. The energetics of sensing process was calculated by Density Functional Theory (DFT) studies. We also fabricate a thin film polymer sensor which was able to detect nitroaromatic vapors with high selectivity. This opens up the possibility of building a low-cost and light-weight nitroaromatic explosives sensor for field use.

7.
Acc Chem Res ; 52(7): 1865-1876, 2019 07 16.
Artigo em Inglês | MEDLINE | ID: mdl-31016963

RESUMO

Nature is intrinsically able to control kinetics, conversion, and selectivity of biochemical processes by means of confined reaction environments such as enzyme pockets, bilayer membranes, micelles, vesicles, cells, or bioorganic frameworks. The main reason for this fact is the optimal molecular alignment and restricted motion of reactant molecules compared to those found in bulk solution. Under this inspiration, a number of synthetic photo-nanoreactors based on supramolecular self-assembled systems have been developed during the last decades, including mesoporous inorganic materials, microemulsions, micelles, vesicles, lipid bilayer foams, polyelectrolyte nanoparticles, etc. In a broader sense, nanoreactor technology constitutes nowadays a promising tool to enhance organic synthesis under sustainable reaction conditions. In general, nanoreactors change the essential properties of the molecules within them, thus affecting their chemical reactivity. Among the nanoreactor-like systems described in the literature to facilitate photochemical processes, the more recent use of viscoelastic supramolecular gels, typically made of low-molecular-weight (LMW) compounds self-assembled through noncovalent interactions, as compartmentalized reaction media is particularly appealing due to the versatility of these materials in terms of fabrication, properties, and processability. Furthermore, the high specific surface areas found in supramolecular gels, their stimuli-responsive reversibility, good diffusion properties enhancing the interactions between reactants and the three-dimensional (3D) porous network, functional tunability, and blocking effect of external oxygen are some of the most important features that can benefit photoinduced processes carried out in confined gel media. Not surprisingly, the efficiency of photochemical processes inside gel media is largely dependent on the type of reaction, characteristics of the gel network, solvent nature, reactant properties, and reaction conditions. Thus, the main focus of this Account is to provide a concise overview of the most relevant examples reported by us and others in order to illustrate the main advantages associated with the emerging use of gel-based materials as nonconventional reaction media to facilitate and control photochemical reactions. In particular, photodimerization, triplet-triplet annihilation upconversion (TTA-UC) coupled to single electron transfer (SET), photooxidation, photoreduction, and trifluoromethylation reactions will be illustrated during the discussion. These examples suggest that gel-based media can provide a versatile platform for the discovery of new reaction pathways and facilitate the way that photochemical reactions are traditionally carried out in academia and industry in terms of reaction conditions and required infrastructure. In addition, the use of physical or chemical gels as reaction systems may also accelerate high-throughput screening of photocatalysts. Overall, a judicious choice of gelators, reactants, solvent, and reaction conditions for the assembly of these gelators is crucial for controlling conversion, kinetics, and selectivity of intragel photoinduced processes.

8.
Polymers (Basel) ; 10(9)2018 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-30960966

RESUMO

The human nervous system lacks an inherent ability to regenerate its components upon damage or diseased conditions. During the last decade, this has motivated the development of a number of strategies for nerve regeneration. However, most of those approaches have not been used in clinical applications till today. For instance, although biomaterial-based scaffolds have been extensively used for nerve reparation, the lack of more customized structures have hampered their use in vivo. This highlight focuses mainly on how 3D bioprinting technology, using polymeric hydrogels as bio-inks, can be used for the development of new nerve guidance channels or devices for peripheral nerve cell regeneration. In this concise contribution, some of the most recent and representative examples are highlighted to discuss the challenges involved in various aspects of 3D bioprinting for nerve cell regeneration, specifically when using polymeric hydrogels.

9.
Langmuir ; 33(40): 10588-10597, 2017 10 10.
Artigo em Inglês | MEDLINE | ID: mdl-28918640

RESUMO

Supramolecular host-guest interactions between randomly methylated ß-cyclodextrin (RM ß-CD) and side-chain phenylalanine (Phe) and Phe-Phe dipeptide-based homopolymers have been employed for the amplification of fluorescence emission of otherwise weakly fluorescent amino acid Phe. The host-guest complex has been characterized by 1H and 13C NMR spectroscopy, two-dimensional rotating-frame overhauser spectroscopy, Fourier-transform infrared spectroscopy, UV-visible spectroscopy, and fluorescence spectroscopy. To gain insights into the origin of fluorescence in homopolymers, density functional theory calculations were performed where phenyl moieties inside the less polar core of ß-CD were observed to form a π-π coupled complex resulting in an enhanced emission. Furthermore, the complex-forming ability of Phe, the guest molecule, has been employed in tuning the cloud point temperature (TCP) of statistical copolymers derived from side-chain Phe/Phe-Phe-based methacrylate monomers and N-isopropylacrylamide. By varying the co-monomer feed ratios in the statistical copolymer and hence the concentration of RM ß-CD throughout the polymer chain, host-guest interaction-assisted broad tunability in TCP of the supramolecular polymeric complex has been achieved.


Assuntos
Fenilalanina/química , Substâncias Macromoleculares , Polímeros , Espectrometria de Fluorescência , Temperatura
10.
Chemistry ; 23(60): 15156-15165, 2017 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-28850744

RESUMO

Poly[2-(methacryloyloxy)ethyl oleate-co-pentafluorophenyl methacrylate] [P(MAEO-co-PFPMA)] random copolymers with oleate and pentafluorophenyl side-chain pendants were synthesized. These copolymers were utilized as dual-reactive polymeric scaffolds in a range of post-polymerization modification strategies involving thiol-ene and para-fluoro-thiol substitution, amidation, trans-esterification, and epoxidation followed by amidation. The 2-(methacryloyloxy)ethyl oleate (MAEO) functional handle in the copolymer is open to functionalization at its internal double bond through thermally initiated thiol-ene reaction, whereas the pentafluorophenyl moiety of the pentafluorophenyl methacrylate (PFPMA) unit undergoes para-fluoro-thiol substitution under basic conditions at room temperature. By means of these modification approaches, the P(MAEO-co-PFPMA) copolymer was orthogonally ligated with thiol compounds having, for example, alkyl, hydroxyl, and protected amine functional groups. Furthermore, different functional groups such as benzyl, allyl, methacrylate, pyrene, and water-soluble poly(ethylene glycol) were easily introduced into the side chain of the P(MAEO-co-PFPMA) copolymer by amidation, trans-esterification, and epoxidation followed by amidation. Functionalization of both the reactive pendants with the various organic substituents was confirmed by 1 H and 19 F NMR spectroscopy, gel permeation chromatography, and fluorescence spectroscopy.

11.
J Mater Chem B ; 5(6): 1218-1226, 2017 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-32263591

RESUMO

Actin filament dynamics is important for proper cellular functions and is controlled by hundreds of actin binding proteins inside the cells. There are several natural and synthetic compounds that are able to bind actin and alter the actin filament dynamics. Since the actin dynamics changes due to nonspecific electrostatic interactions between negatively charged actin and positively charged proteins, and natural or synthetic compounds, herein we report the synthesis of poly(tert-butyl carbamate (Boc)-l-alanine methacryloyloxyethyl ester) (P(Boc-Ala-HEMA)) homopolymer in a controlled fashion by the reversible addition-fragmentation chain transfer (RAFT) polymerization. Subsequent deprotection of the Boc groups in the homopolymer under acidic conditions resulted in a positively charged polymer with primary amine moieties at the side chains. This cationic polymer (P(NH3 +-Ala-HEMA)), is able to nucleate actin in vitro. The cationic polymer and corresponding partially fluorescence tagged polymer are able to nucleate actin filament in vivo. These polymers are nontoxic to the cultured cells and also stabilize the filamentous actin in vitro.

12.
Langmuir ; 31(34): 9422-31, 2015 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-26259117

RESUMO

An effective strategy has been documented to combine both carbohydrate and amino acid biomolecules in a single synthetic polymeric system via a reversible addition-fragmentation chain transfer (RAFT) polymerization technique. The resultant unique block copolymer was engineered to form uniform micelles with the desired projection of either selective or both amino acid/sugar residues on the outer surface with multivalency, providing pH-based stimuli-responsiveness and/or lectin recognition. The self-assembly process was studied in detail by field emission scanning electron microscopy (FE-SEM), dynamic light scattering (DLS), and UV-visible spectroscopy. The enhanced lectin binding behavior was observed for glyconanoparticles with both amino acid/sugar entities on the shell as compared to the only glycopolymer nanoparticle because of the higher steric hindrance factor in the case of only the glycopolymer nanoparticle. Fluorophore conjugation by postpolymerization functionalization was further exploited by fluorescence spectroscopy for evidencing the lectin recognition process.


Assuntos
Aminoácidos/química , Carboidratos/química , Corantes Fluorescentes/química , Lectinas/química , Polímeros/química , Aminoácidos/síntese química , Carboidratos/síntese química , Corantes Fluorescentes/síntese química , Concentração de Íons de Hidrogênio , Estrutura Molecular , Polímeros/síntese química
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