温度敏感性PVP/CHI共混水凝胶的制备与溶胀性能

制备了戊二醛交联的PVP/CHI共混水凝胶,讨论了CHI∶PVP(质量比)、引发剂用量、交联剂用量、反应温度等主要条件对凝胶溶胀性能的影响.温度敏感性实验表明,凝胶分别在33℃、37℃出现最大平衡溶胀率,即具有多重温度敏感性.随着PVP含量的升高,凝胶在33℃时对温度的敏感程度升高、37℃时对温度的敏感程度降低,交联度增加使凝胶的温度敏感程度降低.另外,PVP含量升高使CHI结晶度降低,进而使PVP/CHI凝胶的玻璃化转变温度Tg降低.     

PVP/PAA共混水凝胶的制备及性能研究

以丙烯酸(AA)为单体,聚乙烯吡咯烷酮(PVP)为添加剂,通过引发剂引发自由基聚合制备了聚乙烯吡咯烷酮/聚丙烯酸(PAA)共混水凝胶,讨论了聚乙烯吡咯烷酮用量、反应温度、引发剂含量及交联剂含量等条件对合成凝胶影响,并研究了其溶胀行为。实验结果表明,在合成过程中,凝胶时间随PVP的含量增多而延长,且乳白色深度逐渐加深;随引发剂的增加,产生乳白色时间及凝胶时间缩短;一定范围内随温度升高可凝胶时间降低;交联剂的用量对凝胶时间无明显影响。在PVP/PAA共混水凝胶体系中,当PVP质量分数为0.6%,PAA质量分数为16.4%,引发剂的质量分数为0.024%,交联剂的质量分数为0.016%时,水凝胶的吸水性最佳,且随体系p H变化,酸性条件下吸水性较差,在碱性条件下吸水性较好;当在Na Cl溶液中溶胀时,水凝胶的吸水性能随盐离子浓度增大而下降且达到一定浓度后,水凝胶的吸水性能趋于稳定,盐离子对其影响微弱。PVP/PAA水凝胶的吸水效率高,且表现出很强的吸水能力,并且具有成本低廉,应用广泛等特点。     

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%。     

磺化纤维素水凝胶电刺激响应行为的研究

以环氧氯丙烷为交联剂,制备了纤维素水凝胶,用浓硫酸对其进行磺酸改性,制备出一种磺化纤维素水凝胶,并研究了该凝胶的溶胀性能、电刺激响应行为。结果表明,该凝胶在NaCl溶液中其平衡溶胀率随NaCl离子强度的增大而减小。在NaCI溶液中于非接触直流电场作用下,凝胶向电场负极弯曲,弯曲速度和应变随外加电压的增加而增大,并随NaCl离子强度的增大于0.03mol／kg处出现最大值、在循环电场作用下,其电刺激响应行为具有良好的可逆性,     

聚乙烯醇-壳聚糖复合水凝胶的溶胀性能

以聚乙烯醇(PVA)和壳聚糖为原料、以戊二醛为交联剂,在醋酸溶液中合成了聚乙烯醇-壳聚糖复合水凝胶,研究了影响水凝胶溶胀性能的多种因素,实验结果表明,该凝胶对pH、离子、温度敏感,且在pH=3.13盐酸溶液、常温下的蒸馏水及8℃蒸馏水中溶胀度较大,分别为1 112.2%、974.2%、1 036.8%,凝胶溶胀度随着干燥温度及干燥时间的增加而减小,聚乙烯醇种类对水凝胶溶胀性能有显著影响,PVA-1788与壳聚糖形成的水凝胶溶胀度最大为2 074.1%。聚乙烯醇-壳聚糖复合水凝胶因具有优良的机械强度、生物相容性及生物降解性,同时又具有pH/离子/温度敏感性,因此日益显示其在生物医学材料等领域的重要性。     

聚乙烯醇水凝胶的制备及其溶胀性能

以硼砂为交联剂,采用化学交联法制备了聚乙烯醇(PVA)水凝胶。通过测试PVA水凝胶的溶胀性能,讨论了聚乙烯醇与交联剂的最佳配比,以及盐浓度、温度、交联剂对其溶胀率的影响。结果表明,随着交联剂用量的增加,PVA水凝胶的溶胀率逐渐增大,当达到最大值时,又随着交联剂的增加而降低。随着盐浓度的增加,PVA水凝胶的溶胀率逐降低。PVA水凝胶没有温度敏感性。     

磺化β-环糊精/PVA凝胶电刺激响应行为的研究

首先将β-环糊精(β-CD)和聚乙烯醇(PVA)用戊二醛交联制成凝胶;然后以浓硫酸作为改性剂,将磺酸根引入凝胶中,制备出一种阴离子型磺化β-CD/PVA凝胶,并对该凝胶的平衡溶胀率、粘接性能和电刺激响应行为等进行了研究。结果表明:该凝胶在Na2SO4水溶液中的平衡溶胀率随离子强度增加而减小;其剪切强度随PVA含量增加呈先升后降态势,并且在w(PVA)=5%时相对最大(3.8 MPa)。在非接触性直流电场作用下,该凝胶在Na2SO4水溶液中弯向电场负极,其弯曲偏转速率和应变随外加电压增加而增大,并且在离子强度为0.15 mol/L时相对最大;在循环电场作用下,该凝胶的电刺激响应行为具有良好的重现性和可逆性。     

BES-Na磺酸型聚氨酯复合水凝胶的制备与性能研究

以N,N-双(2-羟乙基)-2-氨基乙磺酸钠(BES-Na)和二羟甲基丙酸(DMPA)为亲水扩链剂,原位聚合制备了一系列磺酸型水性聚氨酯(SWPU);再将丙烯酰胺(AM)引入SWPU中乳液聚合制备了一系列BES-Na磺酸型聚氨酯复合水凝胶(SWPUH)。采用傅里叶变换红外光谱(FTIR)表征了SWPUH的结构,研究了BES-Na含量对SWPUH水凝胶的溶胀性能、p H敏感性、离子强度敏感性以及力学性能的影响。结果表明,SWPUH6溶胀比最大,为33. 12,且较SWPUH1平衡溶胀比提升了50. 20%; SWPUH水凝胶还具有多重敏感性,BES-Na的加入能改善水凝胶的酸碱稳定性,且在不同离子强度溶液中,仍然具有较高的溶胀性能。另外,SWPUH水凝胶还具有优异的力学性能,其中SWPUH6水凝胶压缩强度达到最大3. 42 MPa,较SWPUH1压缩强度提升了约4. 5倍,拉伸强度最大值为0. 33 MPa,断裂伸长率最大达到了774%,相比SWPUH1分别提升了175%和59. 3%。     

BES-Na磺酸型聚氨酯复合水凝胶的制备与性能研究

以N,N-双(2-羟乙基)-2-氨基乙磺酸钠(BES-Na)和二羟甲基丙酸(DMPA)为亲水扩链剂,原位聚合制备了一系列磺酸型水性聚氨酯(SWPU);再将丙烯酰胺(AM)引入SWPU中乳液聚合制备了一系列BES-Na磺酸型聚氨酯复合水凝胶(SWPUH)。采用傅里叶变换红外光谱(FTIR)表征了SWPUH的结构,研究了BES-Na含量对SWPUH水凝胶的溶胀性能、p H敏感性、离子强度敏感性以及力学性能的影响。结果表明,SWPUH6溶胀比最大,为33. 12,且较SWPUH1平衡溶胀比提升了50. 20%; SWPUH水凝胶还具有多重敏感性,BES-Na的加入能改善水凝胶的酸碱稳定性,且在不同离子强度溶液中,仍然具有较高的溶胀性能。另外,SWPUH水凝胶还具有优异的力学性能,其中SWPUH6水凝胶压缩强度达到最大3. 42 MPa,较SWPUH1压缩强度提升了约4. 5倍,拉伸强度最大值为0. 33 MPa,断裂伸长率最大达到了774%,相比SWPUH1分别提升了175%和59. 3%。     

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.     

Semi‐interpenetrating networks based on poly(N‐isopropyl acrylamide) and poly(N‐vinylpyrrolidone)

Three series of novel semi‐interpenetrating polymer networks, based on crosslinked poly(N‐isopropylacrylamide), PNIPA, and different amounts of the linear poly(N‐vinylpyrrolidone), PVP, were synthesized to improve the mechanical properties and thermal response of PNIPA gels. The effect of the incorporation of the linear PVP into the temperature responsive networks on the temperature‐induced transition, swelling/deswelling behavior, and mechanical properties was studied. Polymer networks with four different crosslinking densities were prepared with varying molar ratios (25/1 to 100/1) of the monomer (N‐isopropylacrylamide) to the crosslinker (N,N′‐methylenebisacrylamide). The hydrogels were characterized by determination of the equilibrium degree of swelling, the dynamic shear modulus and the effective crosslinking density, as well as tensile strength and elongation at break. Furthermore, the deswelling kinetics of the hydrogels was studied by measuring their water retention capacity. The inclusion of the linear hydrophilic PVP in the PNIPA networks increased the equilibrium degree of swelling. The tensile strength of the semi‐interpenetrating networks (SIPNs) reinforced with linear PVP was higher than that of the PNIPA networks. The elongation at break of these SIPNs varied between 22% and 55%, which are 22 – 41% larger than those for pure PNIPA networks. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

High strength thermoresponsive semi‐IPN hydrogels reinforced with nanoclays

Two series of nanoclay reinforced, thermoresponsive hydrogels were prepared, one based on poly(N‐isopropylacrylamide) (PNIPA) and the other on semi‐interpenetrating networks containing PNIPA and poly(N‐vinyl pyrrolidone) (PVP), designated as SIPNs. The gels were crosslinked with 1, 3, and 5 wt % inorganic clay (hectorite) and SIPN gels additionally contained 1 wt % of PVP. The hydrogels were tested in the “as‐prepared state,” i.e., at 10 wt % PNIPA concentration in water and at equilibrium (maximum) swelling. Increasing the concentration of nanoclays increases crosslink density, modulus, tensile strength, elongation (except in equilibrium swollen gels), hysteresis and with decreases in the degree of swelling, broadening of the phase transition region, and a decrease in elastic recovery at high deformations. The presence of linear PVP in the networks increases porosity and the pore size, increases swelling, deswelling rates, and hysteresis, but decreases slightly lower critical solution temperature (LCST), tensile strength, elongation, and elastic recovery. The strongest hydrogels were ones with 10 wt % PNIPA and 5 wt % of nanoclays, displaying tensile strengths of 85 kPa and elongation of 955%. All properties of hydrogels at the equilibrium swollen state are lower than in the as‐prepared state, due to the lower concentration of chains per unit volume, but the trends are preserved. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Properties of Thermoresponsive N-maleyl gelatin-co-P(N-isopropylacrylamide) hydrogel with ultrahigh mechanical strength and self-recovery

Thermo-responsive polymer hydrogels with superior strength and toughness are potential candidate materials in biomedical field, such as drug delivery system and tissue engineering. By introducing maleylgelatin (MAGEL) into the conventional PNIPAAm hydrogel, a series of composite P(NIPAAm-co-MAGEL) hydrogels with combined features were fabricated. Thermo-responsive behaviors, equilibrium swelling ratio (ESR), compression strength, tensile strength (TS) and elongation at-break (E), cyclic compression tests, and thermal stability properties of hydrogels with different amount of MAGEL were investigated. Experimental data indicated that the amount of MAGEL could modulate the mechanical property of the composite hydrogel. With the increase of the MAGEL contents from 0 to 50%, the composite hydrogel with relatively high water content possessed good compressive strength, tensile strength and stretrability. Only when the weight ratio of MAGEL/NIPAAm was 30:70, did the P(NIPAAm-co-MAGEL) have a homogeneous distribution and stable 3D networks which played a significant role in the properties of the hydrogels. Cyclic compression tests results indicated that P(NIPAAm-co-MAGEL) hydrogel had an excellent thermo-reversible ability. This research would expand the scope of the PNIPAAm hydrogel applications.     

Preparation of hydrogels composed of poly(vinyl alcohol) and polyethyleneimine and their electrical response

Semi‐ and full‐interpenetrating polymer network (IPN) hydrogels composed of poly(vinyl alcohol) and polyethyleneimine (PEI) were prepared to investigate the bending behavior under the electric response. To find out the characteristics of the hydrogel in the medium, swelling ratio, and rate and water state of the hydrogels were measured. The swelling ratio of the semi‐IPN hydrogels increased with PEI content in the matrix, whereas that of full‐IPN hydrogels dramatically decrease with increase of PEI contents in the hydrogels. In the water state of hydrogel, the bound water and free water of semi‐IPN hydrogels increased with PEI weight ratio. The full‐IPN hydrogels show the lower free water content in comparison with the semi‐IPN hydrogel. The IPN hydrogels exhibited bending angle change in response to external stimulus such as voltage, the bending angle increased with PEI concentration. In addition, the repeated bending behaviors according to the magnitude of the applied electric field revealed that the bending angle is reversible without collapse of formation of hydrogel in all samples. Thus, the hydrogels will be useful as novel modulation systems in the field of artificial organ and matrix for drug delivery. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

High performances of dual network PVA hydrogel modified by PVP using borax as the structure-forming accelerator

A dual network hydrogel made up of polyvinylalcohol (PVA) crosslinked by borax and polyvinylpyrrolidone (PVP) was prepared by means of freezing-thawing circles. Here PVP was incorporated by linking with PVA to form a network structure, while the introduction of borax played the role of crosslinking PVA chains to accelerate the formation of a dual network structure in PVA/PVP composite hydrogel, thus endowing the hydrogel with high mechanical properties. The effects of both PVP and borax on the hydrogels were evaluated by comparing the two systems of PVA/PVP/borax and PVA/borax hydrogels. In the former system, adding 4.0% PVP not only increased the water content and the storage modulus but also enhanced the mechanical strength of the final hydrogel. But an overdose of PVP just as more than 4.0% tended to undermine the structure of hydrogels, and thus deteriorated hydrogels’ properties because of the weakened secondary interaction between PVP and PVA. Likewise, increasing borax could promote the gel crosslinking degree, thus making gels show a decrease in water content and swelling ratio, meanwhile shrinking the pores inside the hydrogels and finally enhancing the mechanical strength of hydrogels prominently. The developed hydrogel with high performances holds great potential for applications in biomedical and industrial fields.     

Preparation of biodegradable crosslinking agents and application in PVP hydrogel

Firstly, biodegradable crosslinking agents (BCA) were synthesized by ring‐opening polymerization reaction of lactide, four kinds of which with different molecular weights were got by means of changing the ratio of DL ‐lactide(LA) and glycerol(GL). Then a series of poly(N‐vinyl pyrrolidone) (PVP) hydrogels were prepared successfully by radical polymerization of BCA and N‐vinyl pyrrolidone(NVP). Both the ratio of NVP/BCA and the molecular weight of BCA were used to control the performance of PVP hydrogels, which were measured in terms of the ratio of swelling, contact angle, mechanical properties, and biodegradability in vitro. This study showed that increasing both the ratio of NVP/BCA and the molecular weight of BCA resulted in a low crosslinking density of the hydrogels. The crosslinking density played an important role in determining the properties of biodegradable PVP hydrogels. Both the ratio of NVP/BCA and the molecular weight of BCA contributed to high ratio of swelling. A smaller amount of crosslinking agent caused a lower contact angle, while the molecular weight of BCA had little effect on it. In terms of mechanics of hydrogels on both dry and wet conditions, tensile modulus decreased along with decreasing BCA, while the extension at break increased at the beginning and decreased at the end. In the end, measured by mass loss, biodegradability in vitro of hydrogels had two stages: an initial stage with approximately constant loss of mass (stage 1) followed by a stage with rapid mass loss (stage 2). Both increased content and molecular weight of BCA improved the degradation rate of the hydrogels. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1515–1521, 2006     

Synthesis and characteristics of semi‐interpenetrating polymer network hydrogels based on chitosan and poly(hydroxy ethyl methacrylate)

Semi‐interpenetrating polymer networks (semi‐IPNs), composed of chitosan and poly(hydroxy ethyl methacrylate) hydrogels, were prepared and the effects of various pH, temperatures, and an electric‐field on the swollen hydrogels were investigated. The swelling kinetics increased rapidly, reaching equilibrium within 60 min. Semi‐IPN hydrogels exhibited relatively high swelling ratios, 150～350%. The swelling ratio increased when the pH of the buffer was below pH 7 as a result of the dissociation of ionic bonds. Semi‐IPN hydrogels showed electroresponsiveness by shrinking when an electric field was applied. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 86–92, 2005     

亲水-疏水PVP-semi-IPN-PCL水凝胶的制备与溶胀性能

N-乙烯基吡咯烷酮（NVP）在聚己内酯（PCL）的乙酸乙酯溶液中进行自由基聚合，制备了亲水-疏水性聚乙烯吡咯烷酮（PVP）/聚己内酯（PCL）半互穿网络水凝胶（PVP-semi-IPN-PCL）。凝胶中PCL的熔融温度T_m无明显变化，而T_m吸热峰形状随PVP含量变化。凝胶平衡溶胀率（ESR）随PVP含量的升高而增大，结合水量的增大尤其显著。由于“笼蔽效应”，低浓度引发剂时，偶氮二异丁睛（AIBN）引发制备的凝胶ESR低于过氧化苯甲酰（BPO）引发剂。交联剂浓度较低时，以戊二醛交联形成凝胶的ESR较N，N-亚甲基双丙烯酰胺（NMBA）交联形成的凝胶大。浓度较高时，戊二醛交联凝胶ESR较NMBA低。PVP含量（质量）分别为20%、40%、60%、80%时，凝胶溶胀动力学Fick模型中的n值分别为0.854、0.471、0.466、0.253，说明在合适的PVP含量时，凝胶的溶胀动力学符合Fick模型。     

Medicated wound dressings based on poly(vinyl alcohol)/poly(N‐vinyl pyrrolidone)/chitosan hydrogels

Poly(vinyl alcohol)/poly(N‐vinyl pyrrolidone) (PVP)/chitosan hydrogels were prepared by a low‐temperature treatment and subsequent ⁶⁰Co γ‐ray irradiation and then were medicated with ciprofloxacin lactate (an antibiotic) and chitosan oligomer (molecular weight = 3000 g/mol). The gel content, swelling ratio, tensile strength, and crystallinity of the hydrogels were determined. The effects of the chitosan molecular weight, the low‐temperature treatment procedure, and the radiation dosage on the hydrogel properties were examined. The molecular weight of chitosan was lowered by the irradiation, but its basic polysaccharide structure was not destroyed. Repeating the low‐temperature treatment and γ‐ray irradiation caused effective physical crosslinking and chemical crosslinking, respectively, and contributed to the mechanical strength of the final hydrogels. The incorporation of PVP and chitosan resulted in a significant improvement in the equilibrium swelling ratio and elongation ratio of the prepared hydrogels. The ciprofloxacin lactate and chitosan oligomer were soaked into the hydrogels. Their in vitro release behaviors were examined, and they were found to follow diffusion‐controlled kinetics. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2453–2463, 2006     

Preparation and characterization by radiation of poly(vinyl alcohol) and poly(N‐vinylpyrrolidone) hydrogels containing aloe vera

In these studies, hydrogels for wound dressings were made from a mixture of aloe vera and poly(vinyl alcohol) (PVA)/poly(N‐vinylpyrrolidone) (PVP) by freezing and thawing, γ‐Ray irradiation, or a two‐step process of freezing and thawing and γ‐ray irradiation. We examined the physical properties, including gelation, water absorptivity, gel strength, and degree of water evaporation, to evaluate the applicability of these hydrogels for wound dressings. The PVA:PVP ratio was 6:4, the dry weight of aloe vera was in the range 0.4–1.2 wt %, and the solid concentration of the PVA/PVP/aloe vera solution was 15 wt %. We used γ radiation doses of 25, 35, and 50 kGy to expose mixtures of PVA/PVP/aloe vera to evaluate the effect of radiation dose on the physical properties of the hydrogels. Gel content and gel strength increased as the concentration of aloe vera in the PVA/PVP/aloe vera gels decreased and as radiation dose increased and the number of freeze–thaw cycles was increased. The swelling degree was inversely proportional to the gel content and gel strength. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1477–1485, 2003