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1.
Soft Matter ; 2022 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-35748523

RESUMO

Herein, we describe the design and synthesis of a new variety of bio-based hydrogel films using a Cu(I)-catalyzed photo-click reaction. These films exhibited thermal-triggered swelling-deswelling and were constructed by crosslinking a triazide derivative of glycerol ethoxylate and dialkyne structures derived from isosorbide, a well-known plant-based platform molecule. The success of the click reaction was corroborated through infrared spectroscopy (FTIR) and the smooth surface of the obtained films was confirmed by scanning electron microscopy (SEM). The thermal characterization was carried out in terms of thermogravimetry (TGA) and differential scanning calorimetry (DSC), from which the decomposition onset and glass transition temperatures were determined, respectively. Additionally, mechanical properties of the samples were estimated by stress-strain experiments. Then, their swelling and deswelling properties were systematically examined in PBS buffer, revealing a thermoresponsive behavior that was successfully tested in the release of the anticancer drug doxorubicin. We also confirmed the non-cytotoxicity of these materials, which is a fundamental aspect for their potential use as drug carriers or tissue engineering matrices.

2.
Polymers (Basel) ; 13(23)2021 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-34883671

RESUMO

An approach to obtaining various nanostructures utilizing a well-studied polystyrene-b-poly(isoprene) or PS-b-PI diblock copolymer system through chemical modification reactions is reported. The complete hydrogenation and partial sulfonation to the susceptible carbon double bonds of the PI segment led to the preparation of [polystyrene-b-poly(ethylene-alt-propylene)] as well as [polystyrene-b-poly(sulfonated isoprene-co-isoprene)], respectively. The hydrogenation of the polyisoprene block results in enhanced segmental immiscibility, whereas the relative sulfonation induces an amphiphilic character in the final modified material. The successful synthesis of the pristine diblock copolymer through anionic polymerization and the relative chemical modification reactions were verified using several molecular and structural characterization techniques. The thin film structure-properties relationship was investigated using atomic force microscopy under various conditions such as different solvents and annealing temperatures. Small-angle X-ray scattering was employed to identify the different observed nanostructures and their evolution upon thermal annealing.

3.
Polymers (Basel) ; 13(21)2021 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-34771373

RESUMO

Novel hybrid materials of the PB-b-P(o-Bn-L-Tyr) and PI-b-P(o-Bn-L-Tyr) type (where PB: 1,4/1,2-poly(butadiene), PI: 3,4/1,2/1,4-poly(isoprene) and P(o-Bn-L-Tyr): poly(ortho-benzyl-L-tyrosine)) were synthesized through anionic and ring-opening polymerization under high-vacuum techniques. All final materials were molecularly characterized through infrared spectroscopy (IR) and proton and carbon nuclear magnetic resonance (1H-NMR, 13C-NMR) in order to confirm the successful synthesis and the polydiene microstructure content. The stereochemical behavior of secondary structures (α-helices and ß-sheets) of the polypeptide segments combined with the different polydiene microstructures was also studied. The influence of the α-helices and ß-sheets, as well as the polydiene chain conformations on the thermal properties (glass transition temperatures, thermal stability, α- and ß-relaxation) of the present biobased hybrid copolymers, was investigated through differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dielectric spectroscopy (DS). The obtained morphologies in thin films for all the synthesized materials via atomic force microscopy (AFM) indicated the formation of polypeptide fibrils in the polydiene matrix.

4.
Polymers (Basel) ; 13(9)2021 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-33946538

RESUMO

The depolymerization process of PET by glycolysis into BHET monomer is optimized in terms of reaction temperature and time, by carrying out the process under pressure to be faster for reducing the energy required. Almost pure BHET has been obtained by working in a pressure reactor at 3 bar both at 220 and 180 °C after short reaction times, while for longer ones a mixture of oligomers and dimers is obtained. Depending on the potential application required, the obtention of different reaction products is controlled by adjusting reaction temperature and time. The use of a pressure reactor allows work at lower temperatures and shorter reaction times, obtaining almost pure BHET. To the best of our knowledge, except for microwave-assisted procedures, it is the first time in which pure BHET is obtained after such short reaction times, at lower temperatures than those usually employed.

5.
Polymers (Basel) ; 13(3)2021 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-33498200

RESUMO

In this work, polymethacrylates containing sulfonyl and nitrile functional groups were successfully prepared by conventional radical polymerization and reversible addition-fragmentation chain-transfer polymerization (RAFT). The thermal and dielectric properties were evaluated, for the first time, considering differences in their molecular weights and dispersity values. Variations of the aforementioned properties do not seem to substantially affect the polarized state of these materials, defined in terms of the parameters ε'r, ε"r and tan (δ). However, the earlier appearance of dissipative phenomena on the temperature scale for materials with lower molecular weights or broader molecular weight distributions, narrows the range of working temperatures in which they exhibit high dielectric constants along with low loss factors. Notwithstanding the above, as all polymers showed, at room temperature, ε'r values above 9 and loss factors below 0.02, presenting higher dielectric performance when compared to conventional polymer materials, they could be considered as good candidates for energy storage applications.

6.
ACS Appl Mater Interfaces ; 12(11): 13275-13286, 2020 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-32067453

RESUMO

Conductive and flexible bio-based materials consisting of chitosan films coated with conductive poly(3-hexylthiophene) (P3HT) were prepared. Thermal, optical, mechanical, morphological, wettability, and conductive properties were analyzed. In a very simple and effective method of chitosan film modification, a controlled volume of a P3HT solution was deposited onto a previously formed chitosan film, assisted by the spin coating method. Later, P3HT-coated chitosan films were doped by simple contact with an aqueous solution of HAuCl4. The use of HAuCl4 becomes attractive because the reports on the doping process in this type of material using this reagent are still scarce and recent to date. In addition, since this acid is a well-known metal nanoparticle precursor, its use opens new future perspectives for these materials into new applications. The effect of P3HT concentration and doping times on film properties was studied. Attenuated total reflectance spectroscopy and UV-Vis spectroscopy allowed us to demonstrate that the presence of the P3HT coating and its doping induce significant changes in the vibrational modes and optoelectronic properties of samples. Additionally, the images obtained by scanning electron microscopy showed a well-distributed and homogeneous coating on the surface of chitosan films. Measured conductivity values of doped film samples fall in the range from 821.3 to 2017.4 S/m, representing, to the best of our knowledge, the highest values reported in the literature for chitosan/chitin-based materials. Indeed, these values are around or even higher than those obtained for some materials purely consisting of conductive polymers.


Assuntos
Quitosana/química , Materiais Revestidos Biocompatíveis/química , Eletrônica/instrumentação , Tiofenos/química , Cloretos/química , Módulo de Elasticidade , Condutividade Elétrica , Compostos de Ouro/química , Teste de Materiais , Maleabilidade , Molhabilidade
7.
Polymers (Basel) ; 11(2)2019 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-30960301

RESUMO

Materials that have high dielectric constants, high energy densities and minimum dielectric losses are highly desirable for use in capacitor devices. In this sense, polymers and polymer blends have several advantages over inorganic and composite materials, such as their flexibilities, high breakdown strengths, and low dielectric losses. Moreover, the dielectric performance of a polymer depends strongly on its electronic, atomic, dipolar, ionic, and interfacial polarizations. For these reasons, chemical modification and the introduction of specific functional groups (e.g., F, CN and R-S(=O)2-R´) would improve the dielectric properties, e.g., by varying the dipolar polarization. These functional groups have been demonstrated to have large dipole moments. In this way, a high orientational polarization in the polymer can be achieved. However, the decrease in the polarization due to dielectric dissipation and the frequency dependency of the polarization are challenging tasks to date. Polymers with high glass transition temperatures (Tg) that contain permanent dipoles can help to reduce dielectric losses due to conduction phenomena related to ionic mechanisms. Additionally, sub-Tg transitions (e.g., γ and ß relaxations) attributed to the free rotational motions of the dipolar entities would increase the polarization of the material, resulting in polymers with high dielectric constants and, hopefully, dielectric losses that are as low as possible. Thus, polymer materials with high glass transition temperatures and considerable contributions from the dipolar polarization mechanisms of sub-Tg transitions are known as "dipolar glass polymers". Considering this, the main aspects of this combined strategy and the future prospects of these types of material were discussed.

8.
ACS Appl Mater Interfaces ; 10(44): 38476-38492, 2018 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-30346120

RESUMO

This work presents the synthesis of new poly(itaconate)s containing sulfone or nitrile pendant groups through conventional radical polymerization together with their characterization and comparison with poly(methacrylate)s containing identical groups. Structural and thermal characterization has been carried out in terms of Fourier transform infrared spectroscopy, differential scanning calorimetry, nuclear magnetic resonance, and thermogravimetric analysis. Characterized by broad band dielectric spectroscopy (BDS), all polymers showed dielectric constant values between 7 and 10 (at 25 °C and 1 kHz) and relative low dielectric loss values (≈0.02). BDS measurements showed, for all the polymers analyzed, notorious subglass transitions even at temperatures below -100 °C, resulting in a broad temperature interval in which these polymers exhibit high dielectric constant and could work without high losses. Therefore, these materials seem to be good candidates for dielectric applications such as energy storage, among others.

9.
Carbohydr Polym ; 199: 20-30, 2018 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-30143121

RESUMO

The motivation of the present work was the preparation of bio-based thin film nanocomposites with improved dielectric properties using modified nanocellulose and chitosan, both materials known to derive from industrial waste. Cyanoethylation of cellulose nanocrystals (CNC) was achieved through a "green" method for the first time. Then, modified CNCs were incorporated into a chitosan (Chi) matrix, obtaining a homogeneous and flexible material with higher dielectric constant due to the high dipole moment of the nitrile functional group. The value of dielectric constant rises with the content of modified CNCs, from a value of 5.5 for pure chitosan at 25 °C and 1 kHz up to a value of 8.5 for the nanocomposite with 50 wt% at the same conditions. These bio-based nanocomposites show an improvement in their dielectric properties compared to pure chitosan and chitosan/unmodified CNC nanocomposites (for which dielectric constant decreases up to 4.5 at 25 °C and 1 kHz) and can be considered for high-temperature applications. Characterization of cyanoethylated cellulose nanocrystals (CN-CNC) and nanocomposites was carried out by infrared spectroscopy (FT-IR), attenuated total reflectance spectroscopy (ATR), atomic force microscopy (AFM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and solid-state NMR and broad band dielectric spectroscopy (BDS). Tensile tests were developed for mechanical characterization.

10.
Materials (Basel) ; 11(9)2018 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-30149581

RESUMO

In this work, the self-assembled morphologies obtained for poly(styrene-b-butadiene-b-styrene) (SBS) and poly(styrene-b-isoprene-b-styrene) (SIS) ABA-type copolymers were investigated before and after hydrogenation of the polydiene block, which led to poly(styrene-b-ethylene)/poly(ethylene-b-styrene) (SEES) and poly(styrene-b-ethylene)/poly(propylene-b-styrene) (SEPS) copolymers, respectively. The evaluation of different morphologies was carried out using atomic force microscopy (AFM), analyzing the effect of various parameters such as the solvent and polymer concentrations employed for film casting (toluene, cyclohexane, or tetrahydrofurane with concentrations of 1 and 3 wt%), together with that of the annealing treatment (thermal annealing at room temperature, and 60, 80, and 100 °C). The effect of these parameters in combination with the chemical nature of the polydiene block led to different morphologies with different topographic aspects affecting the roughness (Ra) of the film.

11.
J Colloid Interface Sci ; 416: 25-9, 2014 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-24370397

RESUMO

The surface morphology of poly(styrene-b-4 vinyl pyridine) (PS-b-P4VP) diblock copolymer thin films after solvent vapor annealing has been studied. Morphological features can be switched upon exposure to vapors of a solvent selective for one of the blocks. Self-assembled nanostructures such as hexagonal or striped morphologies were obtained varying vapor exposure time. In addition, the effect of the presence of CdSe nanoparticles located in the P4VP block on obtained nanostructures was analyzed. Atomic force microscopy (AFM) was used for morphological characterization of the block copolymer and the nanocomposites. AFM images showed that nanostructuring was different depending on the amount of CdSe nanoparticles, due to the decrease in P4VP chain mobility.


Assuntos
Compostos de Cádmio/química , Dioxanos/química , Nanopartículas Metálicas/química , Poliestirenos/química , Polivinil/química , Compostos de Selênio/química , Solventes/química , Gases/química , Membranas Artificiais , Micelas , Microscopia de Força Atômica , Tamanho da Partícula , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Fatores de Tempo
12.
J Nanosci Nanotechnol ; 13(1): 643-8, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23646790

RESUMO

CdSe nanoparticles with polystyrene (PS) brushes are obtained by "grafting through" technique starting from solely aqueously synthesized nanoparticles. Mercaptoethanol (ME) capped nanoparticles are used to achieve double bond functional groups on the surface by condensation reaction with methacryloxypropyltrimethoxysilane (MPS). PS polymerization starts from these double bonds. Spectroscopic, diffraction and thermal techniques are used to characterize the nanoparticles. Infrared spectroscopy shows the formation of robust bonding between CdSe nanoparticles and the organic ligand, as well as the presence of the functional double bond on the surface of nanoparticles. Thermal analysis reveals changes in thermal properties of PS, as thermal stability of PS in the functionalised nanoparticles is improved. UV-vis and fluorescence measurements show that PS-CdSe nanoparticles exhibit good optical properties and transmission electron microscope (TEM) micrographs shows good level of dispersion of CdSe nanoparticles in a PS matrix.


Assuntos
Compostos de Cádmio/química , Cristalização/métodos , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Poliestirenos/química , Compostos de Selênio/química , Semicondutores , Coloides/síntese química , Radicais Livres , Substâncias Macromoleculares/química , Teste de Materiais , Conformação Molecular , Tamanho da Partícula , Propriedades de Superfície
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