高强度多孔聚乙烯醇水凝胶的制备

为制备兼顾多孔性和高强度的水凝胶,本研究利用循环冷冻和冷冻干燥联用设计和制备了一系列聚乙烯醇水凝胶。从聚乙烯醇溶液的浓度、循环冷冻次数、单次冷冻时长三个方面对水凝胶的力学性能、内部微观形貌、含水量进行了研究。结果表明:以质量分数14%浓度的聚乙烯醇水溶液经过3次循环冷冻过程(16h冷冻,8h解冻)和液氮冷冻冰干后的支架,再经溶胀平衡后得到的PVA水凝胶具有最佳的力学性能,此时PVA水凝胶的拉伸强度为5.74MPa,断裂伸长率为347%;改变循环冷冻次数可有效地调节PVA水凝胶的含水量;水凝胶力学性能提高来源于体系结晶度的增大。     

高浓度聚乙烯醇水凝胶性能研究

利用冷冻-解冻法制备了不同类型高浓度(30wt.%)聚乙烯醇(PVA)水凝胶,研究了PVA水凝胶的溶胀率、拉伸强度和流变特性。结果表明,高浓度PVA水凝胶的溶胀率受PVA的分子量和醇解度影响较大,PVA分子量越大,水凝胶的溶胀率越高;醇解度越高,溶胀率越低。随着冻融循环次数的增加,PVA水凝胶的强度增强;分子量越大,PVA水凝胶的强度反而越弱。在一定的频率范围内,PVA水凝胶的模量随着频率的增加而增加;随着冻融循环次数的增加,PVA水凝胶的储能模量增大。     

具有各向异性结构的聚乙烯醇水凝胶的制备及性能表征

首先对聚乙烯醇（PVA）水溶液进行定向冷冻-解冻制备出具有各向异性结构的PVA水凝胶,然后采用⁶⁰Co-γ射线对其进行辐射交联以提高其热稳定性和力学性能。扫描电子显微镜（SEM）结果显示PVA水凝胶保持了各向异性的微观结构,在平行冷冻方向上具有相对规整的取向结构,在垂直冷冻方向上呈现均匀孔洞结构。热稳定性测试结果表明：辐射剂量在30~70 kGy范围内、定向冷冻次数为1次的PVA水凝胶在60℃热水浴中保持凝胶状态长达10 h以上。对辐射交联PVA水凝胶进行拉伸力学性能测试,凝胶具有各向异性的拉伸性能,且拉伸强度和弹性模量均有提高,辐射剂量为10 kGy、定向冷冻次数为3次的PVA水凝胶（DFT-RC-3-10）在垂直定向冷冻方向上的拉伸强度和弹性模量分别为0.86和0.10 MPa。     

聚乙烯醇/粘土复合凝胶的制备及性能

文章采用冷冻-解冻法和硼酸法完成了聚乙烯醇包埋粘土微球复合材料的制备,进行了复合凝胶的力学性能和溶胀特性的测试,研究比较了不同的制备方法对复合凝胶的影响。结果表明冷冻-解冻法制备的PVA凝胶比硼酸法制备的PVA凝胶承受的拉升强度更大可以达到3.29MPa,添加粘土后的复合凝胶的溶胀性能减弱到原来的一半。     

室温交联PVA水凝胶的制备与性能研究

以环氧氯丙烷为交联剂,采用室温化学交联法制备了聚乙烯醇(PVA)水凝胶,研究了交联温度和交联时间对PVA溶胀性能和力学性能的影响,借助差示扫描量热法(DSC)和扫描电子显微镜(SEM)对PVA水凝胶进行分析表征。结果表明,当交联时间为3d且交联温度为50℃时PVA水凝胶的综合性能最佳。PVA的玻璃化转变温度为-54.50℃,PVA水凝胶中包含有自由水、束缚水和非冷冻水。     

聚乙烯醇/γ-聚谷氨酸多孔水凝胶构建研究

本实验采用天然大分子聚乙烯醇(PVA),γ-聚谷氨酸(γ-PGA)和魔芋葡甘聚糖(KGM)为基材，通过反复冻融的物理交联方法构建出半透明、多孔的聚乙烯醇/γ-聚谷氨酸多孔水凝胶。而后通过改变γ-PGA、KGM、PVA浓度以及pH、反复冻融次数、冷冻温度与冷冻时间等单因素实验，并进行响应面法优化，获得了制备γ-聚谷氨酸/聚乙烯醇多孔水凝胶的最佳工艺。实验结果显示，在γ-PGA、KGM与PVA浓度分别在10%、2.5%以及10%,p H为7，冷冻温度-80℃，冷冻时间4小时，反复冻融次数为3次时，所制得的γ-聚谷氨酸/聚乙烯醇多孔水凝胶拥有最佳的溶胀性能，利用扫描电镜和电子万能材料机检测显示所得凝胶拥有丰富的多孔网络结构和良好的机械性能，其溶胀度可达792.6%并且能保水达48小时，可以满足良好敷料的需求。     

PVA/Fe2O3磁敏感性水凝胶的制备及性能

采用循环冷冻-解冻方法制备了聚乙烯醇(PVA)/Fe2O3磁敏感性水凝胶. 考察了水凝胶的力学性能、溶胀性能和磁敏感性,并用扫描电镜观察了其表面形貌. 结果表明,当Fe2O3含量为1%(w)时,水凝胶的力学性能最好;水凝胶的溶胀度和脱水率随时间增加有相似的变化趋势,都随磁性粒子含量升高而降低;溶胀性能降低其交联程度增加;PVA和Fe2O3相容性较好;水凝胶在3000 Oe的磁场强度下达到饱和,呈现出很强的顺磁性,磁滞损耗较多,表明具有较好的磁敏感性.     

聚乙烯醇/膨润土杂化水凝胶的力学性能和溶胀行为

利用冷冻-解冻法制备了聚乙烯醇/膨润土杂化水凝胶. X射线衍射结果表明,膨润土以剥离形式分布在水凝胶基体中. 研究结果表明,与纯PVA5水凝胶相比,经过5个冷冻-解冻循环制备的含2%(w)膨润土的杂化水凝胶的拉伸模量、拉伸强度和断裂伸长率分别增加了44.0%, 74.2%和25.2%,而溶胀行为与5个循环的纯水凝胶相近. 含0.5%(w)膨润土的杂化水凝胶的拉伸模量和拉伸强度高于基体水凝胶,其在溶胀400 min时的溶胀度高于所有的样品.     

聚丙烯酸钠/聚乙烯醇复合水凝胶的制备及其电响应行为

以过硫酸钾为引发剂,N, N′-二甲基双丙烯酰胺为交联剂结合冷冻-解冻交联,制备了一系列不同配比的聚丙烯酸钠(PAAS)/聚乙烯醇(PVA)互穿网络水凝胶,并用傅里叶红外光谱仪(FTIR)、场发射扫描电子显微镜(SEM)、热失重分析仪(TG)、万能试验机等对其进行表征。结果表明,PVA均匀分散于互穿网络水凝胶中,PVA的加入可以提高PAAS水凝胶的热性能;使PAAS水凝胶的溶胀速率和最大溶胀度减小,在PVA含量达到14%(质量分数,下同)时最低,随后又提高;PVA的加入可以显著提高其力学性能,断裂伸长率和拉伸强度均随PVA含量的增加而增大;PVA的加入提高了互穿网络的电响应灵敏度,且其最佳含量为21%。     

天然纤维素/PVA复合水凝胶的形成机理及力学性能研究

为提高聚乙烯醇(PVA)水凝胶的力学性能,利用Na OH/尿素溶剂,通过物理交联循环冷冻-解冻法,制备了α-纤维素(α-CE)/PVA复合水凝胶。红外光谱,扫描电镜结果表明α-CE与PVA水凝胶基体形成互穿交联网状结构。研究发现α-CE与PVA分子链上的羟基间所形成的氢键使两者牢固结合。力学性能测试表明,复合水凝胶的力学性能得到了大幅度提高,当α-CE含量为4%(wt)时,复合水凝胶的拉伸强度以及在压缩型变量60%下的压缩应力分别由0.09和0.07 MPa提高到0.64和0.52 MPa,比纯PVA水凝胶提高了611%和643%。此外发现,α-CE能明显增强PVA水凝胶的弹性及压缩后的形变回复能力。     

A novel pH‐sensitive and freeze‐thawed carboxymethyl chitosan/poly(vinyl alcohol) blended hydrogel for protein delivery

BACKGROUND: Blended hydrogels are widely applied in medical fields. They can provide many advantages, such as biocompatibility and biodegradability. Many materials and methods are used to obtain blended hydrogels. In this work, carboxymethyl chitosan (CMCS) and poly(vinyl alcohol) (PVA) blended hydrogels were prepared using the freezing and thawing technique. The properties of the hydrogels prepared, i.e. gel fraction, swelling and pH‐responsive behaviors, were investigated. RESULTS: The gel fraction increased with increasing time of freezing and thawing as determined through gravimetric analysis. It was also found that the equilibrium degree of swelling improved obviously due to the addition of CMCS compared to pure PVA hydrogel. The blended hydrogel with composition CMCS/PVA 80/20 (by weight) possessed the highest swelling ratio. The results of the influence of pH values on the swelling behavior showed that minimum swelling ratios of the hydrogels occurred near the isoelectric point of CMCS. Protein release studies were performed under various pH conditions: the release was much slower under acid than under basic conditions. The release showed a burst in the first 15 h and then steadily increased. CONCLUSION: The addition of CMCS can improve the physical properties of pure PVA hydrogels and provide pH sensitivity. It is concluded that PVA hydrogels containing CMCS could be potentially applied as oral delivery systems for protein drugs. Copyright © 2009 Society of Chemical Industry     

Self‐healing hydrogel of poly(vinyl alcohol)/graphite oxide with pH‐sensitive and enhanced thermal properties

Supramolecular hydrogel is a fascinating polymeric material composed of three‐dimensional noncovalent networks with many outstanding properties, especially reversible relevant performances. A self‐healing supramolecular hydrogel of poly(vinyl alcohol)/graphite oxide, with reversible pH responsiveness and good thermal stability, was prepared. The morphology, functional group changes, swelling performance, thermal stability, rheological performance, and self‐healing property of the PVA/GO hydrogel were investigated. A probable mechanism between the components and potential applications were also examined in our study. The experimental results show that the PVA/GO hydrogel was not only self‐healable without external stimulus or addition of any healing agents, but also pH sensitive and with good thermal stability. Green ingredients (PVA and GO) and a simple synthesis method (a freezing/thawing treatment) may pose little threat to the environment and also promote the production of such hydrogels. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46143.     

辐射交联PVA/PVP/胶原复合水凝胶的制备及性能研究

采用辐射交联与冻融循环相结合的方法,将胶原引入聚乙烯醇(PVA)/聚乙烯基吡咯烷酮(PVP)水凝胶体系,制备具有较高生物活性的PVA/PVP/胶原复合水凝胶。通过含水率、溶胀性能、力学性能及微观结构研究胶原对复合水凝胶结构与性能的影响,并优选最佳体系进行体外细胞毒性实验(MTT法)。研究结果表明,复合水凝胶具有均匀分布的三维多孔结构,胶原的添加增大水凝胶网络空间结构,其初始含水率达92%,并在10 h内达到溶胀平衡,但力学性能降低。辐射交联与冻融循环相结合的方法有利于提高胶原水凝胶制备效率,胶原结构不改变,其体外细胞存活率从PVA/PVP水凝胶的77.3%提高到93.8%,细胞相容性提高。     

A Novel Polyvinyl Alcohol-Based Hydrogel with Ultra-Fast Self-Healing Ability and Excellent Stretchability Based on Multi Dynamic Covalent Bond Cross-Linking

A novel self-healing poly(vinyl alcohol) (PVA)-based hydrogel is developed by cross-linking PVA chains through multi dynamic covalent bonds by use of a small cross-linker composed by 4-formylphenylboric acid (FPBA) and lysine (Lys). The dynamic borate-imine-imine-borate bond structure between PVA chains endows the hydrogel excellent stretchability and ultra-fast self-healing ability without external stimulation. The self-healing efficiency can attain 94% and the elongation at break can reach up to near 1000% after only 3 min healing. Moreover, the self-healing of the hydrogel through the contact of two faces from both the same cut position and different cut positions has similar excellent efficiency. The hydrogel with the unusual self-healing performance and stretchability is used as an ideal material in strain sensors monitoring human movement and tiny vibrations caused by human voice. Interestingly, the sensor can continue to function normally after self-healing for only ≈3 s. It is expected that this simple strategy of fabricating self-healing hydrogels with multi dynamic bonds will provide new opportunities in the design and preparation of PVA-based hydrogels to expand their potential applications in sensors and other various fields.     

Rheological investigation of poly(vinyl alcohol)/poly(N-vinyl pyrrolidone) mixtures in aqueous solution and hydrogel state

Rheological behavior of poly(vinyl alcohol) (PVA) and poly(N-vinyl pyrrolidone) (PVP) mixtures in aqueous solutions and hydrogel state was investigated. The complex dependence of the viscosity on PVA/PVP mixture composition could be attributed to cumulative effects of electrostatic interactions, hydrogen bonding or association phenomena. Physical hydrogels were prepared by freezing/thawing method and their viscoelastic properties were followed as a function of number of cryogenic cycles and aging time at 37 °C. From swelling experiments, it was observed that the diffusion of water molecules into the hydrogel pores is Fickian (for low number of cryogenic cycles) and it becomes pseudo-Fickian as the sample is submitted to more than 10 freezing/thawing cycles. PVA/PVP hydrogels obtained by physical interactions present a high degree of tailorability and they are suitable candidates for biomedical applications.     

Self-healing quadruple shape memory hydrogels based on coordination,borate bonds and temperature with tunable mechanical properties

Quadruple shape memory hydrogels were prepared by one-pot in situ copolymerization using acrylamide, acrylic acid, agar, and poly(vinyl alcohol). The hydrogels have multiple reversible shape memory based on the coordination bonds of poly(acrylic acid) with Fe3+, borate bonds based on poly(vinyl alcohol), and hydrogen bonds of agar and poly(vinyl alcohol). The hydrogel demonstrated tunable mechanical properties when the hydrogels immersed in different solutions for various lengths of time. After immersion in the ferric chloride solution, tensile stress and elastic moduli of the hydrogels were enhanced with increasing soaking time. After immersion in the borax solution, tensile stress first increased and then decreased with increasing soaking time. Due to the reversible effect of the borate bond, the hydrogel achieved ultra-fast self-healing. The hydrogel after immersion in borax solution could begin healing in 24 h and healed at 44 h. The tensile stress and tensile strain of the self-healing hydrogel increased when soaking time increased from 48 to 96 h, and tensile stress at healing times of 96 h was nearly as the same as that of the original hydrogel when compared with it. The combination of tunable mechanical properties, efficient recoverability and self-healing abilities coupled with facile preparation endowed the developed hydrogel a high potential for use in biomedical applications.     

Silicon dioxide/poly(vinyl alcohol) composite hydrogels with high mechanical properties and low swellability

Poly(vinyl alcohol) (PVA) hydrogels with tissue-like viscoelasticity, excellent biocompatibility, and hydrophilicity have been considered as promising cartilage replacement materials. However, the low mechanical properties of pure PVA hydrogels limit their applications for bearing complicated loads. Herein, we report silicon dioxide (SiO₂)/PVA composite hydrogels fabricated by fabricated cyclically freezing/thawing the aqueous mixture of PVA and methyltrimethoxysilane (MTMS). MTMS hydrolyzes and forms SiO₂ particles in situ to reinforce PVA hydrogel. Meanwhile, silanol group condenses with hydroxyl groups of PVA and chemically bonds with PVA. The resulting SiO₂/PVA hydrogels exhibit much better mechanical properties than bare PVA hydrogel. In addition, the composite hydrogels keep very low swellable property. This prepared composite hydrogels are promising in a variety of biomedical applications such as artificial articular cartilage, drug delivery, and biosensors. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46895.     

Characterization of PVA/glycerin hydrogels made by <Emphasis Type="Italic">γ</Emphasis>-irradiation for advanced wound dressings

The aim of this study was to investigate the enhanced absorption property of PVA/Glycerin (PVA/Gly) hydrogel for advanced wound dressing. A simple crosslinking method was introduced to prepare the PVA/Gly hydrogels with the use of γ-irradiation. An absorption ratio and thermal properties of the PVA/Gly hydrogels can be controlled by varying the irradiation dose and weight ratio of the PVA/Gly. When the PVA/Gly content was 20/5 wt% and the irradiation dose at 25 kGy, the PVA/Gly hydrogels showed excellent absorption properties (>350%). These results imply that the PVA/Gly hydrogel is highly absorbent and converts wound exudates to the hydrogel matrices that create a moist and clean environment in the wound healing process. Therefore, the PVA/Gly hydrogel prepared by this method can be used as an advanced wound dressing.     

Porous boron nitride nanofibers/PVA hydrogels with improved mechanical property and thermal stability

Polyvinyl alcohol (PVA) hydrogel is a promising material possessing good chemical stability, high water absorption, excellent biocompatibility and biological aging resistant. However, the poor mechanical performance of PVA hydrogel limits its applications. Here we report the utilization of one-dimensional (1D) BN nanofibers (BNNFs) as nanofillers into PVA matrix to prepare a novel kind of BNNFs/PVA composite hydrogel via a cyclic freezing and thawing method. For comparison, the composite hydrogels using spherical BN nanoparticles i.e. BN nanospheres (BNNSs) as fillers were also prepared. The mechanical properties, thermal stabilities and swelling behaviors of the composite hydrogels were investigated in detail. Our study indicates that the mechanical properties of the hydrogels can be improved by adding of BNNFs. After loading of BNNFs into PVA with content of 0.5?wt%, the compressive strength of the composite hydrogel increases by 252% compared with that of pure PVA hydrogel. The tensile performance of BNNFs/PVA composite hydrogels has also been improved. Impressive 87.8% increases in tensile strengths can be obtained with 1?wt% BNNFs added. In addition, with the increase of BNNFs content, the thermal stability and the swelling ratio of hydrogels are increased gradually. The swelling ratio of hydrogel increases by 56.3% with only 1?wt% BNNFs added. In comparison, the improvement effects of the BNNS fillers on the mechanical strengths and swelling ratios are much weaker. The enhanced effects of BNNFs can be ascribed to the strong hydrogen bond interaction between BNNFs and PVA. The high aspect ratios of the nanofibers should also be took into account.