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1.
This work aims at developing an approach to Ru(II)(Tpy)2‐functionalized hydrogels and exploring the coupling of the hydrogels with the Belousov‐Zhabotinsky (BZ) reaction. Based on free radical polymerization, two synthetic routes are developed. The first one is the direct gelation by copolymerization of acrylamide as hydrophilic component and Ru(II)(Tpy)2 as the functional group. The second one is carried out through a combined approach. A terpyridine‐containing hydrogel is first prepared and then post‐functionalized by coordination between Ru(III)(Tpy)Cl3 and terpyridine groups in the hydrogel network. Utilizing the synthetic hydrogels, the reversible redox responsiveness, the coupling with the BZ reaction, the occurrence and the self‐oscillating properties of the BZ reaction in the hydrogel networks are studied. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2214–2222  相似文献   

2.
Engineering three‐dimensional (3D) hydrogels with well‐defined architectures has become increasingly important for tissue engineering and basic research in biomaterials science. To fabricate 3D hydrogels with (sub)cellular‐scale features, two‐photon polymerization (2PP) shows great promise although the technique is limited by the selection of appropriate hydrogel precursors. In this study, we report the synthesis of gelatin hydrolysate vinyl esters (GH‐VE) and its copolymerization with reduced derivatives of bovine serum albumin (acting as macrothiols). Photorheology of the thiol‐ene copolymerization shows a much more rapid onset of polymerization and a higher end modulus in reference to neat GH‐VE. This allowed 2PP to provide well‐defined and stable hydrogel microstructures. Efficiency of the radical‐mediated thiol‐vinyl ester photopolymerization allows high 2PP writing speed (as high as 50 mm s?1) with low laser power (as low as 20 mW). MTT assays indicate negligible cytotoxicities of the GH‐VE macromers and of the thiol‐ene hydrogel pellets. Osteosarcoma cells seeded onto GH‐VE/BSA hydrogels with different macromer relative ratios showed a preference for hydrogels with higher percentage of GH‐VE. This can be attributed both to a favorable modulus and preferable protein environment since gelatin favors cell adhesion and albumin incurs nonspecific binding. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4799–4810  相似文献   

3.
We present novel redox‐responsive hydrogels based on poly(N‐isopropylacrylamide) or poly(acrylamide), consisting of a reversible disulfide crosslinking agent N,N′‐bis(acryloyl)cystamine and a permanent crosslinking agent N,N′‐methylenebisacrylamide for microfluidic applications. The mechanism of swelling/deswelling behavior starts with the cleavage and reformation of disulfide bonds, leading to a change of crosslinking density and crosslinking points. Raman and ultraviolet‐visible spectroscopy confirm that conversion efficiency of thiol–disulfide interchange up to 99%. Rheological analysis reveals that the E modulus of hydrogel is dependent on the crosslinking density and can be repeatedly manipulated between high‐ and low‐stiffness states over at least 5 cycles without significant decrease. Kinetic studies showed that the mechanical strength of the gels changes as the redox reaction proceeds. This process is much faster than the autonomous diffusion in the hydrogel. Moreover, cooperative diffusion coefficient (Dcoop) indicates that the swelling process of the hydrogel is affected by the reduction reaction. Finally, this reversibly switchable redox behavior of bulky hydrogel could be proven in microstructured hydrogel dots through short‐term photopatterning process. These hydrogel dots on glass substrates also showed the desired short response time on cyclic swelling and shrinking processes known from downsized hydrogel shapes. Such stimuli‐responsive hydrogels with redox‐sensitive crosslinkers open a new pathway in exchanging analytes for sensing and separating in microfluidics applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2590–2601  相似文献   

4.
In this work, we report a versatile infrared laser ignited frontal polymerization technique for the fabrication of a series of poly(DMC‐co‐HPA) hydrogels (DMC = methacryloxyethyltrimethyl ammonium chloride, HPA = hydroxypropyl acrylate). Because the method is based on the exothermic reaction, no further energy is required in the reaction once it is initiated. Moreover, we have found the polymerization process is a pure frontal polymerization model without involving any other reaction process. The dependence of frontal velocity and temperature on the reaction time is thoroughly discussed. The as‐prepared hydrogels are pH‐responsive and their maximum equilibrium swelling ratio could reach ~3,890%. Also, the as‐prepared poly(DMC‐co‐HPA) hydrogels capable of adsorption/desorption switching performance can be utilized for heavy metal ion removal in wastewater treatments. Interestingly, the hydrogels can float on the water surface after intaking heavy metal ions by the combination of kerosene and polyoxyethylene sorbitan monolaurate (Tween 20) in hydrogel components, greatly enhancing treatment efficiency. We believe the method described herein to rapidly construct functional hydrogels with the ability to remove heavy metal ions may find unique applications in emergency processing of water pollution. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2085–2093  相似文献   

5.
Lactide polymerization using zirconium(IV) acetylacetonate [Zr(acac)4] as an initiator was investigated. In the reaction between Zr(acac)4 and the monomer molecule, lactide deprotonation and the release of acetylacetone occurred. The structures of the obtained complexes were analyzed with high‐resolution NMR spectroscopy. A computational method was used to calculate the hypothetical structures. The role of the obtained complexes in the initiation of polymerization and the reaction of chain growth was proposed. The influence of the reaction temperature on the structures of the complexes was investigated. Polylactide chain growth proceeded by an insertion‐coordination mechanism. The polymer chain grew on one ligand, which was formed in advance from a deprotonated lactide. The molecular masses of the obtained polymers were the same as the theoretical masses and were directly proportional to the reaction conversion. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1886–1900, 2004  相似文献   

6.
Stimuli‐responsive polypeptides are receiving much attention for drug delivery systems and tissue engineering scaffolds; however, it is challenging to construct multiple‐responsive polypeptides and one‐component polymeric hydrogels. Herein, a novel type of triple redox/temperature‐responsive diselenide‐containing poly(methoxydiethylene glycol‐l ‐glutamate) homopolypeptide was facilely synthesized by selenocystamine‐initiated ring‐opening polymerization in DMF at 30 °C, and their chemical structures and physical properties were fully characterized by means of 1H NMR, GPC, FT‐IR, WAXD, and CD. They self‐assembled into spherical micelles in aqueous solution, which possess a lower critical solution temperature, redox‐responsiveness inherited from diselenide bond, and the triple stimuli‐sensitive self‐assembly behaviors, as characterized by means of turbidity, DLS, TEM, and zeta potential measurements. The diselenide‐containing homopolypeptides formed supramolecular hydrogels at room temperature, exhibiting a thermal gel–sol transition. The rheological tests evidence that the mechanical modulus of the hydrogel is independent of angular frequency within 100 rad/s and at 25 °C, in which the storage modulus of G′ is order of magnitude greater than the loss modulus of G″, displaying a solid‐like elastic behavior. Moreover, the mechanical modulus of the hydrogel can be tuned by changing the chain length of the homopolypeptide, the 10‐mM 1,4‐dithiothreitol (DTT) reduction, and 1 mM H2O2 oxidation, respectively. Consequently, this work provides a simple strategy to fabricate triple‐stimuli responsive polypeptide micelles and one‐component hydrogels. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1067–1077  相似文献   

7.
Tough hydrogels have great potentials in soft robotics, artificial muscles, tissue replacement, and so on. Here we introduce novel tough hydrogels crosslinked by triblock copolymer (F127DA) micelles and metal coordination. The gels showed outstanding tensile strength (∼1–11 MPa), toughness (∼4–32 MJ m−3), and excellent self‐recovery properties (∼56.8–87.2% toughness recovery in 9 min at room temperature). The mechanical and self‐recovery properties could be manipulated by varying contents of micelles and/or COO groups. Dynamic mechanical analysis of the hydrogels revealed apparent activation energy and relaxations for both physical interactions. In situ small‐angle X‐ray scattering measurements on hydrogels upon stretching revealed micelle deformations. XPS measurements on hydrogels before and after stretching revealed significant changes in the binding energy of Fe3+ ions in the gels, suggesting the rupture of coordination bonds. The experimental results strongly suggest a synergistic effect from the micelle‐crosslinking and Fe3+–COO coordination on the strength, toughness, and self‐recovery of the hydrogels. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 865–876  相似文献   

8.
A nanocomposite (NC) hydrogel crosslinked by inorganic Laponite XLG was successfully synthesized via in situ free radical polymerization of monomers N,N‐diethylacrylamide and (2‐dimethylamino) ethyl methacrylate (DMAEMA). Polymerization was carried out at room temperature due to the accelerating effect of DMAEMA. The as‐prepared hydrogels displayed controlled transformation in optical transmittance and volume in response to small diversification of environmental factors, such as temperature and pH. The compressive strength of swollen D6:1G6 hydrogels was as high as 2219 kPa while compressive strain was 95%. Cyclic compression measurement exhibited good elastic properties of NC hydrogels. This work provides a facile method for fabricating stimuli‐responsive hydrogels with superior mechanical property. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 876–884  相似文献   

9.
The aqueous solution behavior and thermoreversible gelation properties of pyridine‐end‐functionalized poly(ethylene glycol)–poly(L ‐lactide) (PEG–(PLLA)8–py) star block copolymers in the presence of coordinating transition metal ions were studied. In aqueous solutions, the macromonomers self‐assembled into micelles and micellar aggregates at low concentrations and formed physically crosslinked, thermoreversible hydrogels above a critical gel concentration (CGC) of 8% w/v. In the presence of transition metal ions like Cu(II), Co(II), or Mn(II), the aggregate dimensions increased. Above the CGC, the gel–sol transition shifted to higher temperatures due to the formation of additional crosslinks from intermolecular coordination complexes between metal ions and pyridine ligands. Furthermore, as an example, PEG–(PLLA)8–py hydrogels stabilized by Mn(II)–pyridine coordination complexes were more resistant against degradation/dissolution when placed in phosphate buffered saline at 37 °C when compared with hydrogels prepared in water. Importantly, the stabilizing effect of metal–ligand coordination was noticeable at very low Cu(II) concentrations, which have been reported to be noncytotoxic for fibroblasts in vitro. These novel PEG–(PLLA)8–py metallo‐hydrogels, which are the first systems to combine metal–ligand coordination with the advantageous properties of PEG–PLLA copolymer hydrogels, are appealing materials that may find use in biomedical as well as environmental applications like the removal of heavy metal ions from waste streams. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

10.
A double hydrogen bonding (DHB) hydrogel is constructed by copolymerization of 2‐vinyl‐4,6‐diamino‐1,3,5‐triazine (hydrophobic hydrogen bonding monomer) and N,N‐dimethylacrylamide (hydrophilic hydrogen bonding monomer) with polyethylene glycol diacrylates. The DHB hydrogels demonstrate tunable robust mechanical properties by varying the ratio of hydrogen bonding monomer or crosslinker. Importantly, because of synergistic energy dissipating mechanism of strong diaminotriazine (DAT) hydrogen bonding and weak amide hydrogen bonding, the DHB hydrogels exhibit high toughness (up to 2.32 kJ m−2), meanwhile maintaining 0.7 MPa tensile strength, 130% elongation at break, and 8.3 MPa compressive strength. Moreover, rehydration can help to recover the mechanical properties of the cyclic loaded–unloaded gels. Attractively, the DHB hydrogels are responsive to CO2 in water, and demonstrate unprecedented CO2‐triggered shape memory behavior owing to the reversible destruction and reconstruction of DAT hydrogen bonding upon passing and degassing CO2 without introducing external acid. The CO2 triggering mechanism may point out a new approach to fabricate shape memory hydrogels.  相似文献   

11.
Novel electro‐conductive and mechanically‐tough double network polymer hydrogels (E‐DN gels) were synthesized by polymerization of 3, 4‐ethylenedioxythiophene in the presence of a double network hydrogel (DN gel) matrix. The E‐DN gels showed not only excellent mechanical performance, having a fracture stress of 1.4–2.1 MPa, but also electrical conductivity as high as 10?3 S cm?1, both under dry and water‐swollen states. The fracture stress and fracture energy of the E‐DN gel was increased by 1.7 and 3.4 times, respectively, as compared with the DN gel. From scanning electron microscope and AFM observations, it was found that electro‐conductive poly(3,4‐ethylenedioxythiophene) (PEDOT) was incorporated into DN gel matrix, apparently due to the formation of a poly‐ion complex with sulfonic acid group of the DN gel network. Thus, PEDOT incorporated into the DN gel matrix greatly improves not only electronic conductivity, but also mechanical properties, reinforcing the double network gel matrix. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012  相似文献   

12.

New poly[Acrylamide/N‐vinyl pyrrolidone/3‐(2‐hydroxyethyl carbamoyl)acrylic acid], poly [AAm/NVP/HECA], chelating hydrogels with different composition of HECA monomer have been prepared via free radical solution polymerization using N,N‐methylene bisacrylamide as a crosslinker. The hydrogels obtained were loaded with metal ions and characterized by FT‐IR spectroscopy, Scanning Electron Microscope (SEM) and Thermogravimatric analysis (TGA). The removal of Cu2+ and Ni2+ from aqueous solutions by the hydrogel was examined by a batch equilibrium method. The influence of treatment time, pH, initial concentration of the metal ions and HECA content in the feed compositions on the amount of adsorbed metal ions was studied. Swelling of the hydrogel was also carried out in distilled water and metal ion solutions. The removal of the metal ions followed the following order: Ni2+>Cu2+. The amount of metal ions removed increased with increasing HECA content in the feed composition, treatment time, pH of the medium and initial concentration of metal ions. The desorption of metal ions were carried out using 1 N HCl and 0.5 N H2SO4. The poly[AAm/NVP/HECA] hydrogels could be used many times without significantly decreasing their adsorption capacity.  相似文献   

13.
Stimulus response of photopolymerized 1% and 0.5% N,N′‐methylene bisacrylamide (MBA) crosslinked 10% polyacrylamide (PAAm) hydrogels was studied in nitric acid. The hydrogels swelled exponentially to saturation in 13 h due to the osmotic pressure arising from diffusion of ions in to the gel. MBA (0.5%) gels swell more with larger time constant than 1% MBA gels due to lower bulk modulus. Diffusion coefficient of nitric acid in the hydrogel and polymer‐solvent interaction parameter were estimated from the swelling behavior and discussed. At longer times, the hydrogels deswelled linearly in nitric acid due to molecular modification of amide group by acidic hydrolysis. Degree of swelling and deswelling increase with nitric acid concentration. Raman and FTIR investigations revealed the formation of carboxylic acid due to acidic hydrolysis. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 710–720, 2008  相似文献   

14.
Soft tissues, such as fat and skin, present high flexibility and are capable of withstanding large deformation in various functions. Hydrogels that can resemble the mechanical performance of soft tissue are unique and widely demanded. In this study, micellar hydrogels based on biocompatible poly(l ‐glutamic acid) (PLGA) were designed with the enhanced capacity to bear large deformation. Amphipathic triblock copolymer poly(ethylene glycol) acrylate‐co‐poly(ε‐caprolactone)‐co‐poly (ethylene glycol) acrylate (APEG‐PCL‐APEG) with two terminal double bonds was synthesized and self‐assembled into micelles. At the same time, graft copolymers, poly(l ‐glutamic acid)‐g‐hydroxyethyl methacrylate (PLGA‐g‐HEMA) with double bonds were synthesized. APEG‐PCL‐APEG micelles and PLGA‐g‐HEMA were mixed to construct micellar hydrogel via radical polymerization. The crystalline structure and hydrophobic aggregation of copolymers (APEG‐PCL‐APEG) were found to associate with PCL molecular weight. Due to the hydrophobic stress dissipation and crystalline structure of the micelles, the softness and toughness of hydrogels were promoted, exhibiting a 25% increase in ultimate strain. Moreover, the micellar hydrogels were able to load proteins with long‐term retention. In addition, under dynamic mechanical stimulation, the release of proteins could be accelerated. Besides, the micellar hydrogels also supported rabbit adipose‐derived stem cells (rASCs) growth, thus exhibiting the potential toward soft tissue engineering. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1115–1125  相似文献   

15.
Catalytic precursors Ti(IV) and Zr(IV) complexes bearing cyclopentadienyl and substituted cyclopentadienyl anionic ligands, bonded to phenyl or substituted phenyl through an isopropylidene bridge have been utilized in the polymerization of propene and styrene and in ethylene‐styrene copolymerization. In the presence of trichloro[(1,2,3,4,5‐η)‐1‐(1‐methyl‐1‐phenylethyl)‐2,4‐cyclopentadien‐1‐yl]titanium (LTiCl3) we have obtained either partially isotactic (chain‐end type) or atactic poly‐(propylene), and either atactic or syndiotactic polystyrene depending on the reaction temperature. [1‐Methyl‐1‐naphthylethyl‐2‐inden‐1‐yl]titanium(IV) behaves like (LTiCl3) in styrene polymerization, while it affords metal‐controlled partially isotactic poly(propylene), as well as the corresponding zirconium compounds. The experimental data are tentatively explained by the temperature dependence of coordination of the bridged aryl group of the ligand.  相似文献   

16.
Water soluble monomer like sodium p‐styrene sulfonate (SSS) is copolymerized with hydrophobic and reactive monomer glycidyl methacrylate (GMA). The polymerization proceeds as dispersion and forms gels. The gel forming nature prevails even with other hydrophobic and hydrophilic monomers to form ternary polymeric systems. The swelling is dependent on polymer composition as well as the treatment history of polymers. SSS also induces ring opening of GMA to form 1,2‐diols as confirmed independently by various model reactions. The ability of hydrogels to absorb various dyes indicates that owing to the anionic nature, hydrogels absorb cationic dyes nearly quantitatively. Because of their strong affinity to cationic species these hydrogel forming polymers are potentially useful in water purification applications as well as purification of proteins. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 626–634  相似文献   

17.
Poly(N‐acryloyl glycinamide) (PNAGA)/poly(N‐isopropyl acrylamide) (PNIPAAm) interpenetrating network (IPN) hydrogels were made by UV‐light initiated radical polymerization in two‐steps. The IPN hydrogels showed a double thermoresponsive behavior due to the combination of PNIPAAm (thermophobic) and PNAGA (thermophilic) networks. Increasing the content of the thermophobic PNIPAAm network leads to a change from a broad thermophilic volume phase transition temperature of PNAGA to a thermophilic–thermophobic‐type dual transition for the prepared IPN. Due to the double thermoresponsive character of the IPN gels, the mechanical properties are dependent upon temperature as demonstrated by performing tensile tests in water at 15 and 50 °C. Furthermore, the IPN hydrogels were characterized using turbidity measurements, SEM, and the determination of the equilibrium swelling ratio. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 539–544  相似文献   

18.
The synthesis and characterization of thermoresponsive hydrogels on the basis of N‐isopropylacrylamide (IPAAm) copolymers crosslinked with biodegradable poly(amino acids) are described. This hydrogel was prepared with two kinds of reactive IPAAm‐based copolymers containing poly(amino acids) as the side‐chain groups and activated ester groups. We introduced the graft chains by decarboxylation polymerization of amino acid N‐carboxyanhydrides initiated from lateral amino groups in the PIPAAm copolymer. The hydrogels easily crosslinked with degradable poly(amino acid) chains by only mixing the copolymer aqueous solutions. The gelling method in this study would provide some of the following innovative features: (1) no necessary removal of unreacted monomers and so forth, (2) simpler loading of drugs into the hydrogels (only mixing when gelling), and (3) easier insertion into the body. On the basis of the swelling ratio measurement of the hydrogel, large volume changes dependent on temperature changes were observed. Moreover, the enzymatic temperature‐dependent degradation was confirmed. The results suggested that these hydrogels could be used for an injectable or implantable matrix of temperature‐modulated drug release. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 779–787, 2003  相似文献   

19.
pH‐sensitive nanoclay composite hydrogels based on N‐isopropylacrylamide (NIPA) were synthesized by copolymerization with cationic and anionic comonomers. Laponite nanoclay particles served as multifunctional crosslinkers, producing hydrogels with exceptionally high mechanical strengths, as measured by elongation at break. Cationic copolymer gels based on NIPA and dimethylaminoethylmethacrylate were prepared by aqueous free radical polymerization, adopting a procedure reported by Haraguchi (Adv Mater 2002, 14, 1120–1124). Without modification, this technique failed to produce anionic copolymer gels of NIPA and methacrylic acid (MAA), due to flocculation of clay particles. Three methods were conceived to incorporate acidic MAA into nanoclay hydrogels. First, NIPA was copolymerized with sodium methacrylate under dilute conditions, producing hydrogels with good pH‐sensitivity but weak mechanical characteristics. Second, NIPA was copolymerized with methyl methacrylate, which was then hydrolyzed to generate acid sidegroups, yielding hydrogels that were much stronger but less pH sensitive. Third, NIPA was copolymerized with MAA following modification of the nanoclay surface with pyrophosphate ions. The resulting hydrogels exhibited both strong pH‐sensitivities at 37 °C and excellent tensile properties. Optical transparency changed during polymerization, depending on hydrophobicity of the components. This work increases the diversity and functionality of nanoclay hydrogels, which display certain mechanical advantages over conventionally crosslinked hydrogels. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6630–6640, 2008  相似文献   

20.
Development of self‐healing hydrogels with thermoresponse is very important for artificial smart materials. In this article, the self‐healing hydrogels with reversible thermoresponses were designed through across‐linking‐induced thermoresponse (CIT) mechanism. The hydrogels were prepared from ketone group containing copolymer bearing tetraphenyl ethylene (TPE) and cross‐linked by naphthalene containing acylhydrazide cross‐linker. The mechanical property, light emission, self‐healing, and thermo‐response of the hydrogels were investigated intensively. With regulation of the copolymer composition, the hydrogels showed thermoresponse with the LCST varied from above to below body temperature. At the same time, the hydrogels showed self‐healing property based on the reversible characteristic of the acylhydrazone bond. The hydrogel also showed temperature‐regulated light emission behavior based on AIE property of the TPE unit. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 869–877  相似文献   

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