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1.
Macromol Biosci ; 24(9): e2400120, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-38801012

RESUMO

Mucus lines the epithelial cells at the biological interface and is the first line of defense against multiple viral infections. Mucins, the gel-forming components of mucus, are high molecular weight glycoproteins and crucial for preventing infections by binding pathogens. Consequently, mimicking mucins is a promising strategy for new synthetic virus inhibitors. In this work, synthetic mucin-inspired polymers (MIPs) as potential inhibitors of herpes simplex virus 1 (HSV-1) are investigated. By using a telechelic reversible addition-fragmentation chain-transfer (RAFT) polymerization technique, a new dendronized polysulfate p(G1AAm-OSO3)PDS with an amide-backbone similar to the native mucin glycoproteins is synthesized. p(G1AAm-OSO3)PDS shows mucin-like elongated fiber structure, as revealed in cryo-electron microscopy (cryo-EM) imaging, and its HSV-1 inhibition activity together with its previously reported methacrylate analogue p(G1MA-OSO3)PDS is tested. Both of the sulfated MIPs show strong HSV-1 inhibition in plaque reduction assays with IC50 values in lower nanomolar range (<3 × 10-9 m) and demonstrate a high cell compatibility (CC50 > 1.0 mg mL-1) with lower anticoagulant activity than heparin. In addition, the prophylactic and therapeutic activity of both MIPs is assessed in pre- and post-infection inhibition assays and clearly visualize their high potential for application using fluorescent microscopy imaging of infected cells.


Assuntos
Antivirais , Herpesvirus Humano 1 , Mucinas , Herpesvirus Humano 1/efeitos dos fármacos , Mucinas/química , Mucinas/metabolismo , Antivirais/farmacologia , Antivirais/química , Humanos , Animais , Polímeros/química , Polímeros/farmacologia , Chlorocebus aethiops , Células Vero , Herpes Simples/tratamento farmacológico , Herpes Simples/virologia
2.
Materials (Basel) ; 16(23)2023 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-38068092

RESUMO

The presented work deals with the photocuring of telechelic macromonomers derived from plant-based fatty acids to obtain a soft polymer network. Compositions were made by mixing macromonomers with three different concentrations (0.5, 1, and 2%) of two type I photoinitiators (Omnirad 2022 and Omnirad 819). All formulations were then subjected to photopolymerization studies by applying UV-assisted differential scanning calorimetry (UV-DSC) measurements at isothermal conditions at 37 °C with a narrow light source wavelength of 365 nm and irradiation (light intensity) of 20 and 50 mW/cm2. The percentage conversions, reaction orders, and constants were estimated based on autocatalytic Sestak-Berggen and Avrami models. In this work, for the first time, the influence of the curing conditions on the photopolymerization process, such as the photoinitiator concentration, light intensity, and oxygen presence/absence, were investigated for these novel systems. The results indicated significant differences between the two commercially available photoinitiators and their effects on photopolymerization kinetics. The maximum reaction rate was found to be considerably higher for Omnirad 2022 (which is a blend of three different compounds), especially at a lower light intensity, i.e., 20 mW/cm2, compared to Omnirad 819. However, it led to lower maximum conversion in an air atmosphere. The dynamic thermomechanical analysis (DMTA) revealed that light intensity, photoinitiator concentration, and oxygen presence had a strong effect on the storage modulus and loss modulus values. It was concluded that the chemical structure of the photoinitiator and curing conditions had a strong effect on the photopolymerization kinetics and properties of the prepared soft polymer networks.

3.
ACS Appl Mater Interfaces ; 15(23): 28430-28441, 2023 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-37264775

RESUMO

Semiaromatic polyamides are used for metal replacement in advanced engineering applications to reduce weight and improve efficiency, but their range of application is limited by their inherent lack of ductility and toughness. Here, we combined semiaromatic polyamide poly(hexamethylene terephthalamide-co-isophthalamide) (PA6TI) with up to 30 wt % amine-terminated polyethylene (PE(NH2)2) by high-temperature melt compounding, which was suggested to lead to the formation of PA-PE block copolymers at the interface between the PE(NH2)2 and the PA6TI. This resulted in PA6TI/PE(NH2)2 blends with smaller, more uniform particle sizes than in PA6TI blended with nonfunctional PE or the commercial impact modifier, maleic anhydride-functionalized styrene-ethylene-butylene-styrene (SEBS) under the same conditions. The PA6TI/PE(NH2)2 blends and the corresponding glass fiber-reinforced composites consequently showed significantly greater increases in room-temperature tensile ductility and fracture energy with respect to unmodified PA6TI, as well as maintained mechanical stability at high temperatures, and only modest decreases in stiffness and strength, even at high PE(NH2)2 contents. These improvements were attributed to the crystallinity of the PE(NH2)2 particles and to improved morphological stabilization and matrix-particle adhesion, consistent with the presence of PA-PE block copolymer at the matrix-particle interfaces.

4.
ACS Appl Mater Interfaces ; 15(24): 29140-29148, 2023 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-37303115

RESUMO

The development of promising solid-state lithium batteries has been a challenging task mainly due to the poor interfacial contact and high interfacial resistance at the electrode/solid-state electrolyte (SSE) interface. Herein, we propose a strategy for introducing a class of covalent interactions with varying covalent coupling degrees at the cathode/SSE interface. This method significantly reduces interfacial impedances by strengthening the interactions between the cathode and SSE. By adjusting the covalent coupling degree from low to high, an optimal interfacial impedance of 33 Ω cm-2 was achieved, which is even lower than the interfacial impedance using liquid electrolytes (39 Ω cm-2). This work offers a fresh perspective on solving the interfacial contact problem in solid-state lithium batteries.

5.
Carbohydr Polym ; 299: 120170, 2023 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-36876785

RESUMO

Functional Pickering emulsions that depend on the interparticle interactions hold promise for building template materials. A novel coumarin-grafting alginate-based amphiphilic telechelic macromolecules (ATMs) undergoing photo-dimerization enhanced particle-particle interactions and changed the self-assembly behavior in solutions. The influence of self-organization of polymeric particles on the droplet size, microtopography, interfacial adsorption and viscoelasticity of Pickering emulsions were further determined by multi-scale methodology. Results showed that stronger attractive interparticle interactions of ATMs (post-UV) endowed Pickering emulsion with small droplet size (16.8 µm), low interfacial tension (9.31 mN/m), thick interfacial film, high interfacial viscoelasticity and adsorption mass, and well stability. The high yield stress, outstanding extrudability (n1 < 1), high structure maintainability, and well shape retention ability, makes them ideal inks for direct 3D printing without any additions. The ATMs provides an increased capacity to produce stable Pickering emulsions with tailoring their interfacial performances and, providing a platform for fabricating and developing alginate-based Pickering emulsion-templated materials.

6.
Polymers (Basel) ; 15(3)2023 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-36771783

RESUMO

Nano-sized particles functionalised with short single-stranded (ss)DNAs can act as detectors of complementary DNA strands. Here we consider tri-block-copolymer-based, self-assembling DNA-coated nanoparticles. The copolymers are chemically linked to the DNA strands via azide (N3) groups. The micelles aggregate when they are linked with complementary ssDNA. The advantage of such block-copolymer-based systems is that they are easy to make. Here we show that DNA functionalisation results in inter-micellar attraction, but that N3-groups that have not reacted with the DNA detector strands also change the phase behaviour of the tri-block polymer solution. We studied the triblock copolymer, Pluronic® F108, which forms spherical micelles in aqueous solutions upon heating. We find that the triblock chains ending with either an N3 or N3-DNA complex show a dramatic change in phase behaviour. In particular, the N3-functionalisation causes the chain ends to cluster below the critical micelle temperature (CMT) of pure F108, forming flower-micelles with the N3-groups at the core, while the PPO groups are exposed to the solvent. Above the CMT, we see an inversion with the PPO chains forming the micellar core, while the N3-groups are now aggregating on the periphery, inducing an attraction between the micelles. Our results demonstrate that, due to the two competing self-assembling mechanisms, the system can form transient hydrogels.

7.
Chemistry ; 29(16): e202203849, 2023 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-36511092

RESUMO

This work describes a versatile and efficient condensation polymerization route to aliphatic polyesters by organo-catalyzed (4-dimethylaminopyridine) transesterification reactions between an activated pentafluorophenyl-diester of adipic acid and structurally different diols. By introducing "monofunctional impurity" or "stoichiometric imbalance," this methodology can afford well-defined end-functionalized polyesters with predictable molecular weights and narrow dispersity under mild conditions without any necessity for the removal of the byproducts to accelerate the polymerization reaction, which remains a major challenge in conventional polyester synthesis with non-activated diesters. Wide substrate scope with structurally different monomers and the synthesis of block copolymers by chain extension following either ring-opening polymerization or controlled radical polymerization have been successfully demonstrated. Some of the polyesters synthesized by this newly introduced approach show high thermal stability, crystallinity, and enzymatic degradation in aqueous environments.

8.
J Polym Sci (2020) ; 60(13): 2000-2007, 2022 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-35915665

RESUMO

The control of chain-ends is fundamental in modern macromolecular chemistry for directed one-to-one bioconjugation and the synthesis of advanced architectures such as block copolymers or bottlebrush polymers and the preparation of advanced soft materials. Polyphosphazenes are of growing importance as elastomers, biodegradable materials and in biomedical drug delivery due to their synthetic versatility. While controlled polymerization methods have been known for some time, controlling both chain-ends with high fidelity has proven difficult. We demonstrate a robust synthetic route to hetero and homo α,ω-chain-end functionalized polyphosphazenes via end-capping with easily accessible, functionalized triphenylphosphine-based phosphoranimines. A versatile thiol-ene "click"-reaction approach then allows for subsequent conversion of the end-capped polymers with various functional groups. Finally, we demonstrate the utility of this system to prepare gels based on homo α,ω-chain-end functionalized polyphosphazenes. This development will enhance their progress in various applications, particularly in soft materials and as degradable polymers.

9.
Polymers (Basel) ; 14(14)2022 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-35890654

RESUMO

Hydroxyl-terminated natural rubber (HTNR) is a product of interest for making natural rubber (NR) easy and versatile for use in a wide range of applications. Photochemical degradation using a TiO2 film that has been deposited on a glass substrate is one of the fascinating methods of producing HTNR. Nevertheless, light energy is wasted during the photodegradation process because a glass substrate has a cutoff for ultraviolet light. To enhance the effectiveness of the process, a quartz substrate was coated with the TiO2 film for photochemical breakdown. X-ray diffraction (XRD) spectroscopy and atomic force microscopy (AFM) were applied to investigate the TiO2 deposited on glass and quartz substrates. In addition, the influence of several factors, such as rubber and surfactant concentrations, on the reaction was investigated. After the reaction, the properties of the rubber products, including intrinsic viscosity, molecular weight, and microstructure, were determined. A unique diffraction peak for the anatase (101) phase could be observed in the TiO2 film deposited on the quartz substrate, resulting in photochemical activity and photocatalytic efficiency significantly higher than those of the substrate made of glass. In the scenario of deproteinized NR (DPNR) latex containing 10% DRC, 20% w/w H2O2, and TiO2 film coated on a quartz substrate, the HTNR could be manufactured effectively.

10.
J Colloid Interface Sci ; 600: 174-186, 2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34015510

RESUMO

HYPOTHESIS: Polysiloxanes are becoming new trend in self-cleaning (oil- and water-repellent) applications due to their low-cost and environmentally friendly nature. Lower phase separation of polysiloxanes in coating matrix is critical to obtain excellent self-cleaning properties. We hypothesize that telechelic polysiloxanes can bind to coating matrix at both ends and thus will suppress phase separation of polysiloxane as compared to hemi-telechelic analog and thus will offer excellent self-cleaning properties. EXPERIMENT: Eight PDMS additives were prepared via the free-radical polymerization of telechelic and hemi-telechelic methacryloxypropyl-based PDMS precursors with methylmethacrylate (MMA) and glycidylmethacrylate (GMA). The compositions of the prepared polysiloxane additives were optimized to obtain excellent self-cleaning performance. FINDINGS: Our breakthrough development confirms that telechelic polysiloxanes (PDMS-T) incorporated into epoxy-based anti-smudge coatings outperform hemi-telechelic polysiloxanes (PDMS-HT) by offering excellent repellency against difficult to repel liquids. These breakthrough findings will vertically advance Science and innovations in the self-cleaning field by offering robust guidelines for choosing suitable polysiloxane for self-cleaning applications.


Assuntos
Siloxanas , Água , Polimerização
11.
Angew Chem Int Ed Engl ; 59(51): 22983-22988, 2020 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-32840964

RESUMO

The synthesis of stereoregular telechelic polypropylene (PP) and their use to access triblock amphiphilic copolymers with the PP block located in the center is described. The strategy consists of selectively copolymerizing propylene and a di-functional co-monomer (1,3-diisopropenylbenzene) to yield a α,ω-substituted polypropylene. Initiation of the copolymerization favors insertion of DIB over propylene; propagation steps favor insertion of propylene. Termination via a chain-transfer reaction yields the terminal unsaturation of the polymer. The telechelic polypropylene is then converted into α,ω-hydroxyl-terminated polypropylene and used as a macroinitiator for the synthesis of triblock copolymers. Water-soluble amphiphilic triblock polymers are also synthesized. The use of catalytic reactions simultaneously provides the stereocontrol of the polypropylene and high productivity (multiple chains of block copolymer per metal center).

12.
Int J Pharm ; 586: 119605, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32650112

RESUMO

Targeting bioactives selectively to diseased sites is one of the most challenging aspects of cancer therapy. Herein, fabrication of colonic enzyme-responsive dextran based oligoester crosslinked nanoparticles is reported for the controlled release of 5-fluorouracil (5-FU) - an anticancer drug. The 5-FU drug loaded nanoparticles (DNPs, size ~237 ± 25 nm, ζ-potential -17.0 ± 3 mV) were developed by the in-situ crosslinking of dextran with a bifunctional telechelic oligoester followed by the physical drug encapsulation via nanoprecipitation. Drug encapsulation efficiency and drug loading capacity of DNPs were found to be ~76% (±0.1) and ~8% (±0.1), respectively. The DNPs were demonstrated to release the encapsulated drug selectively in the presence of dextranase enzyme. The in vitro release kinetics assay revealed that the DNPs released about 75% (±4) of the entrapped drug within 12 h of incubation with dextranase enzyme. No drug was released in a control experiment where DNPs were exposed to pH conditions encountered in the stomach and small intestine. Moreover, the treatment of HCT116 colon cancer cell line with the developed DNPs highlighted its biocompatibility as well as dextranase triggered cytotoxicity. The developed system offers an avenue to reduce the non-specific cytotoxicity of the encapsulated 5-FU, and a colon specific delivery of the encapsulated drug in response to the dextranase enzyme.


Assuntos
Fluoruracila , Nanopartículas , Colo , Preparações de Ação Retardada , Dextranos , Portadores de Fármacos , Sistemas de Liberação de Medicamentos
13.
Front Chem ; 8: 11, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32047737

RESUMO

Pyranose dehydrogenases (PDHs; EC 1.1.99.29; AA3_2) demonstrate ability to oxidize diverse carbohydrates. Previous studies of these enzymes have also uncovered substrate-dependent regioselectivity, along with potential to introduce more than one carbonyl into carbohydrate substrates. Enzymatic oxidation of carbohydrates facilitates their further derivatization or polymerization into bio-based chemicals and materials with higher value; accordingly, PDHs that show activity on xylooligosaccharides could offer a viable approach to extract higher value from hemicelluloses that are typically fragmented during biomass processing. In this study, AbPDH1 from Agaricus bisporus and AmPDH1 from Leucoagaricus meleagris were tested using linear xylooligosaccharides, along with xylooligosaccharides substituted with either arabinofuranosyl or 4-O-(methyl)glucopyranosyluronic acid residues with degree of polymerization of two to five. Reaction products were characterized by HPAEC-PAD to follow substrate depletion, UPLC-MS-ELSD to quantify the multiple oxidation products, and ESI-MSn to reveal oxidized positions. A versatile method based on product reduction using sodium borodeuteride, and applicable to carbohydrate oxidoreductases in general, was established to facilitate the identification and quantification of oxidized products. AbPDH1 activity toward the tested xylooligosaccharides was generally higher than that measured for AmPDH1. In both cases, activity values decreased with increasing length of the xylooligosaccharide and when using acidic rather than neutral substrates; however, AbPDH1 fully oxidized all linear xylooligosaccharides, and 60-100% of all substituted xylooligosaccharides, after 24 h under the tested reaction conditions. Oxidation of linear xylooligosaccharides mostly led to double oxidized products, whereas single oxidized products dominated in reactions containing substituted xylooligosaccharides. Notably, oxidation of specific secondary hydroxyls vs. the reducing end C-1 depended on both the enzyme and the substrate. For all substrates, however, oxidation by both AbPDH1 and AmPDH1 was clearly restricted to the reducing and non-reducing xylopyranosyl residues, where increasing the length of the xylooligosaccharide did not lead to detectable oxidation of internal xylopyranosyl substituents. This detailed analysis of AbPDH1 and AmPDH1 action on diverse xylooligosaccharides reveals an opportunity to synthesize bifunctional molecules directly from hemicellulose fragments, and to enrich for specific products through appropriate PDH selection.

14.
Macromol Rapid Commun ; 41(18): e2000320, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33463837

RESUMO

New functional initiators for the cationic ring-opening polymerization of 2-alkyl-2-oxazolines are described to introduce a thiol moiety at the α terminus. Both tosylate and nosylate initiators carrying a thioacetate group are obtained in multigram scale, from commercial reagents in two steps, including a phototriggered thiol-ene radical addition. The nosylate derivative gives access to a satisfying control over the cationic ring-opening polymerization of 2-ethyl-2-oxazoline, with dispersity values lower than 1.1 during the entire course of the polymerization, until full conversion. Cleavage of the thioacetate end group is rapidly achieved using triazabicyclodecene, thereby leading to a mercapto terminus. The latter gives access to a new subgeneration of α-functional poly(2-oxazoline)s (butyl ester, N-hydroxysuccinimidyl ester, furan) by Michael addition with commercial (meth)acrylates. The amenability of the mercapto-poly(2-ethyl-2-oxazoline) for covalent surface patterning onto acrylated surfaces is demonstrated in a microchannel cantilever spotting (µCS) experiment, characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary-ion mass spectrometry (ToF-SIMS).


Assuntos
Acrilatos , Compostos de Sulfidrila , Cátions , Oxazóis , Polimerização
15.
J Colloid Interface Sci ; 529: 588-598, 2018 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-30031286

RESUMO

HYPOTHESIS: Hydrophobically modified ethoxylated urethane polymers (HEURs) are widely used to control the rheological profile of formulated particulate dispersions through associative network formation, the properties of which are perturbed by the presence of surfactants. At high polymer concentrations and in the presence of surfactants, it is hypothesised that the dominant factors in determining the rheological profile are the number and composition of the mixed hydrophobic aggregates, these being defined by the number and distribution of the hydrophobic linkers along the polymer backbone, rather than the end-group hydrophobe characteristics per se that dominate the low polymer concentration behaviour. EXPERIMENTS: Three different HEUR polymers with formulae (C6-L-(EO100-L)9-C6, C10-L-(EO200-L)4-C10 and C18-L-(EO200-L)7-C18 (where L = urethane linker, Cn = hydrophobic end-group chain length, and EO = ethylene oxide block) have been studied in the absence and presence of SDS employing techniques that quantify (a) the bulk characteristics of the polymer surfactant blend, (b) the structure and composition of the hydrophobic domains, (c) the dynamics of the polymer and surfactant, and (d) the polymer conformation. Collectively, these experiments demonstrate how molecular-level interactions between the HEURs and sodium dodecylsulfate (SDS) define the macroscopic behaviour of the polymer/surfactant mixture. FINDINGS: Binding of the SDS to the polymer via two mechanisms - monomeric anti-cooperative and micellar cooperative - leads to surfactant-concentration-specific macroscopic changes in the viscosity. Binding of the surfactant to the polymer drives a conformational rearrangement, and an associated redistribution of the polymer end-groups and linker associations throughout the hydrophobic domains. The composition and size of these domains are sensitive to the polymer architecture. Therefore, there is a complex balance between polymer molecular weight, ethylene oxide block size, and number of urethane linkers, coupled with the size of the hydrophobic end-groups. In particular, the urethane linkers are shown to play a hitherto largely neglected but important role in driving the polymer association.

16.
Macromol Rapid Commun ; 39(19): e1800154, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-29675835

RESUMO

Monofunctional or telechelic polyethylenes (PEs) carrying phosphonic acid end groups are obtained from functional PE produced by catalyzed chain growth (CCG) on magnesium. CCG is first used to produce iodo-end-functionalized PE (PE-I) that is efficiently turned into phosphonate end-functionalized PE (PE-P(O)(OEt)2 ) in the presence of triethylphosphite through the Michaelis-Arbuzov reaction. A simple treatment of the resulting PE-P(O)(OEt)2 with bromotrimethylsilane leads to the targeted phosphonic acid end-functionalized PE (PE-P(O)(OH)2 ) for the first time. Vinyl-end-functionalized analogs (Vin-PE-P(O)(OEt)2 ) are produced using vinyl-end-functionalized PE-I (Vin-PE-I) recently obtained through CCG. A cross-metathesis reaction is then employed to couple Vin-PE-P(O)(OEt)2 and produce after treatment with bromotrimethylsilane the corresponding unprecedented α-ω-(diphosphonic acid) telechelic PE ((OH)2 (O)P-PE-P(O)(OH)2 ).


Assuntos
Ácidos Fosforosos/química , Polietilenos/química , Polietilenos/síntese química
17.
Macromol Biosci ; 18(4): e1700389, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29512268

RESUMO

Telechelic antimicrobial poly(2-oxazoline)s with quaternary ammonium (quat) end groups are shown to be potent antimicrobial polymers against Gram-positive bacterial strains. In this study, the activity against the Gram-negative bacterium Escherichia coli is additionally implemented by hydrolyzing the poly(2-methyl-2-oxazoline) with two quart end groups to poly(ethylene imine) (PEI). The resulting telechelic polycations are active against Staphylococcus aureus and E. coli. The contribution of the PEI backbone is determined by measuring the antimicrobial activity in the presence of calcium ions. The influence of PEI on the overall activity strongly depends on the molecular weight and increases with higher mass. The PEI dominates the activity against E. coli at lower masses than against S. aureus. The quart end groups require an alkyl substituent of dodecyl or longer to dominate the antimicrobial activity. Additionally, PEI and quart end groups act synergistically.


Assuntos
Anti-Infecciosos/farmacologia , Escherichia coli/efeitos dos fármacos , Oxazóis/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Anti-Infecciosos/síntese química , Anti-Infecciosos/química , Cálcio/metabolismo , Escherichia coli/patogenicidade , Humanos , Interações Hidrofóbicas e Hidrofílicas , Iminas/síntese química , Iminas/química , Iminas/farmacologia , Testes de Sensibilidade Microbiana , Oxazóis/síntese química , Oxazóis/química , Polietilenos/síntese química , Polietilenos/química , Polietilenos/farmacologia , Polímeros/síntese química , Polímeros/química , Staphylococcus aureus/patogenicidade
18.
Molecules ; 23(2)2018 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-29438313

RESUMO

The use of thermo-reversible Lewis Pair (LP) interactions in the formation of transient polymer networks is still greatly underexplored. In this work, we describe the synthesis and characterization of polydimethylsiloxane/polystyrene (PDMS/PS) blends that form dynamic Lewis acid-Lewis base adducts resulting in reversible crosslinks. Linear PS containing 10 mol % of di-2-thienylboryl pendant groups randomly distributed was obtained in a two-step one-pot functionalization reaction from silyl-functionalized PS, while ditelechelic PDMS with pyridyl groups at the chain-termini was directly obtained via thiol-ene "click" chemistry from commercially available vinyl-terminated PDMS. The resulting soft gels, formed after mixing solutions containing the PDMS and PS polymers, behave at room temperature as elastomeric solid-like materials with very high viscosity (47,300 Pa·s). We applied rheological measurements to study the thermal and time dependence of the viscoelastic moduli, and also assessed the reprocessability and self-healing behavior of the dry gel.


Assuntos
Compostos de Boro/química , Ácidos de Lewis/química , Bases de Lewis/química , Poliestirenos/química , Siloxanas/química , Química Click , Elasticidade , Géis , Reologia , Temperatura , Viscosidade
19.
Polymers (Basel) ; 10(11)2018 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-30961166

RESUMO

Epoxide- and oxetane-α,ω-telechelic (co)polyolefins have been successfully synthesized by the tandem ring-opening metathesis polymerization (ROMP)/cross-metathesis (CM) of cyclic olefins using Grubbs' second-generation catalyst (G2) in the presence of a bifunctional symmetric alkene epoxide- or oxetane-functionalized chain-transfer agent (CTA). From cyclooctene (COE), trans,trans,cis-1,5,9-cyclododecatriene (CDT), norbornene (NB), and methyl 5-norbornene-2-carboxylate (NBCOOMe), with bis(oxiran-2-ylmethyl) maleate (CTA 1), bis(oxetane-2-ylmethyl) maleate (CTA 2), or bis(oxetane-2-ylmethyl) (E)-hex-3-enedioate (CTA 3), well-defined α,ω-di(epoxide or oxetane) telechelic PCOEs, P(COE-co-NB or -NBCOOMe)s, and P(NB-co-CDT)s were isolated under mild operating conditions (40 or 60 °C, 24 h). The oxetane CTA 3 and the epoxide CTA 1 were revealed to be significantly more efficient in the CM step than CTA 2, which apparently inhibits the reaction. Quantitative dithiocarbonatation (CS2/LiBr, 40 °C, THF) of an α,ω-di(epoxide) telechelic P(NB-co-CDT) afforded a convenient approach to the analogous α,ω-bis(dithiocarbonate) telechelic P(NB-co-CDT). The nature of the end-capping function of the epoxide/oxetane/dithiocarbonate telechelic P(NB-co-CDT)s did not impact their thermal signature, as measured by DSC. These copolymers also displayed a low viscosity liquid-like behavior and a shear thinning rheological behavior.

20.
Macromol Rapid Commun ; 38(22)2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-29024134

RESUMO

(Bis)furan-telechelic, low-molar-mass polybutadienes and polyisoprenes are synthesized by controlled degradation of high molar mass polymers and chain-end modifications yielding difunctional, trifunctional, or tetrafunctional polymers. Addition of a bismaleimide to the liquid-modified polymer leads to the formation of a thermoreversible elastomeric network based on the Diels-Alder chemistry for the trifunctional or tetrafunctional polymers, whereas only chain extension occurs for the bifunctional one. Dynamic mechanical analyses or tensile tests are performed on the networks and reveal a similar behavior for polyisoprene and polybutadiene with nevertheless quite different Young modulus or strain at break. The retro Diels-Alder reaction occurs upon heating, allowing the remolding of the used elastomer. The remolded network exhibits the same mechanical properties as the initial network, showing an efficient material recyclability.


Assuntos
Butadienos/química , Elastômeros/química , Reação de Cicloadição , Módulo de Elasticidade , Elastômeros/síntese química , Furanos/química , Maleimidas/química , Resistência à Tração
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