NVP接枝壳聚糖水凝胶的合成与溶胀性能

合成了N-乙烯基吡咯烷酮（NVP）接枝壳聚糖（CHI）水凝胶,讨论了NVP/CHI、引发剂、交联剂、聚合温度、乙酸浓度等因素对接枝率及凝胶溶胀性能的影响,NVP∶CHI为6时,接枝率达到300%以上. 溶胀温度、pH值、盐浓度等对凝胶溶胀性能的影响实验表明,凝胶表现出温度敏感性,在40 ℃出现最大平衡溶胀率,并观察到一级相转变;在中性或弱酸性介质中溶胀性能较好;与PVP凝胶相比,NVP接枝CHI凝胶表现出反聚电解质效应. 溶胀动力学研究表明,在溶胀前期,CHI含量较高时,凝胶趋向于非Fick溶胀,说明除了溶剂扩散外,凝胶网络链段弛豫、水分子与凝胶网络间及凝胶高分子链段间相互作用对凝胶溶胀性能的影响至关重要;CHI含量较高时则趋向于Fick溶胀.     

交联聚N-乙烯基吡咯烷酮的合成研究

阐述了采用交联剂N,N-亚甲基双丙烯酰胺(NMBA)与N-乙烯基吡咯烷酮共聚,合成N-乙烯基吡咯烷酮的交联聚合物交联聚N-乙烯基吡咯烷酮(PVPP)。总结出PVPP的最佳合成路线为:以5%磷酸氢二钠和5%硫酸钠的水溶液为溶剂,偶氮二异庚腈为引发剂,交联剂选用NMBA,在N2保护下70℃反应90min,干燥后得到凝胶体积可控、残单低、吸水性能强的PVPP颗粒。     

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.     

聚己内酯的化学交联及其形状记忆行为

以聚己内酯二醇、衣康酸酐和对甲苯磺酸为主要原料,采用熔融酯化法合成了PCL-IA(双键功能化的聚己内酯二醇)预聚体;然后以过氧化二异丙苯(DCP)为引发剂、TMPTA(三羟甲基丙烷三丙烯酸酯)为PCL-IA的交联剂,制得交联PCL(聚己内酯)材料。着重探讨了DCP掺量、交联时间和交联温度等对交联度的影响,进而对交联PCL材料的形状记忆行为进行了表征。研究结果表明:随着凝胶含量的增加,交联PCL材料的交联度增大、形状记忆回复率(Rr)和形状固定率(Rf)均明显提高。     

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。     

PCL/PVP共混膜的制备及其性能研究

利用溶液浇铸法制备了聚ε-己内酯(PCL)/聚乙烯吡咯烷酮(PVP)共混膜,分析了PCL/PVP共混膜的结晶性能、相容性、力学性能、亲水性和生物降解性能。结果表明:PVP的加入对PCL的结晶晶型无影响,但产生了稀释作用,两者可以相容且在共混过程中未发生化学反应;一定含量的PVP有助于增强共混膜的力学性能,PVP的质量分数为20%时,PCL/PVP共混膜力学性能最佳;随着PVP含量的增加,共混膜与水的接触角减小,吸水率逐步增大,PCL的亲水性得到改善;PCL/PVP共混膜在磷酸盐缓冲液中的失重率随PVP含量的增加而增大,且共混膜的失重率逐渐由PCL主导过渡到PVP主导,加入脂肪酶可加速PCL/PVP共混膜的降解。     

聚乙烯吡咯烷酮/壳聚糖共混水凝胶的制备与水的状态

以戊二醛作为交联剂,制备了聚乙烯吡咯烷酮（PVP）/壳聚糖（CHI）共混水凝胶,共混物的玻璃化转变温度T_g随CHI含量的升高而升高,SEM图谱观察到PVP/CHI凝胶表面呈现随CHI∶PVP比而变化的微相分离.凝胶溶胀率随着PVP含量升高、PVP分子量降低、CHI脱乙酰度增大而升高.DSC分析表明,非冷冻状态下,CHI∶PVP为1∶2时,游离水、可冻结结合水、非冻结结合水含量分别为42.7%、43.3 %、14.0 %;CHI∶PVP为1∶8时,凝胶中含非冻结结合水少,DSC曲线上只有一个明显的失水吸热峰,由游离水与可冻结结合水叠加而成.-123℃冷冻条件下凝胶的DSC升温曲线在0、38、53℃观察到一组明显的焓化峰,这是由于低温时冻结为结晶相的游离水、可冻结结合水,随温度升高吸热又转化为游离水、可冻结结合水所致.     

pH响应PAAm-g-PEG/PVP半互穿网络水凝胶的制备以及溶胀动力学

采用硝酸铈胺-聚乙二醇为氧化-还原引发体系,N,N-亚甲基双丙烯酰(N,N-MBA)为交联剂,通过简单的自由基聚合法,设计合成了一种聚(丙烯酰胺-g-聚乙二醇)/聚乙烯吡咯烷酮PAAm-g-PEG/PVP接枝交联结构的半互穿网络水凝胶。研究了它们在不同pH值缓冲溶液中的溶胀与扩散行为以及溶胀动力学;并采用红外光谱和热分析系统对其结构和热性能进行了分析测量。实验结果表明:水凝胶的溶胀行为和扩散模式取决于溶液的pH值。随着缓冲溶液pH值增加,平衡溶胀率减小;在不同的缓冲溶液中理论最大吸水量S∞与实验值基本相一致。水凝胶的溶胀行为可以通过选择加入不同分子量大小的PEG来调节和控制。     

电子束辐照对形状记忆聚己内酯材料性能影响

在使用电子束辐照实现聚己内酯(PCL)交联过程中,研究了辐照剂量及交联助剂三羟甲基丙烷三丙烯酸酯(TMPTA)用量对PCL材料交联程度的影响.采用熔融挤出及注塑成型方法制备了TMPTA质量分数为0％～2％的PCL板材.对几种PCL板材施加10～50 kGy的辐照后,通过分析PCL材料的凝胶含量确认其交联程度,发现PCL...     

PAAm／PEG／PVP半互穿网络水凝胶的制备、表征及茶碱释放研究．

以N,N-亚甲基双丙烯酰胺（N,N-MBA）为交联剂、过硫酸钾（KPS）为引发剂·通过丙烯酰胺（AAm）、聚乙二醇（PEG）和聚乙烯吡咯烷酮（PVP）发生共聚反应制备具有半互穿网络结构的水凝胶PAAm／PEG／PVP。采用红外光谱（FTIR）、热重分析（TG）对水凝胶的结构和热学性质进行了分析,研究了中性条件下水凝胶的溶胀性能,并进一步研究了其负栽茶碱在不同缓冲溶液中的释放行为。     

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     

Swelling properties of CMC‐g‐poly (AAm‐co‐AMPS) superabsorbent hydrogel

A series of biopolymer‐based superabsorbent hydrogels based on carboxymethyl cellulose has been prepared by free‐radical graft copolymerization of acrylamide and 2‐acrylamido‐2‐methylpropan sulfonic acid (AMPS) in aqueous solution using methylenebisacrylamide as a crosslinking agent and ammonium persulfate as an initiator. The effect of variables on the swelling capacity such as: acrylamide/AMPS weight ratio, reaction temperature, and concentration of the initiator and crosslinker were systematically optimized. The results indicated that with increasing the amount of AMPS, the swelling capacity is increased. FT‐IR spectroscopy and scanning electron microscope analysis were used to confirm the hydrogel structure. Swelling measurements of the synthesized hydrogels in different salt solutions indicated considerable swelling capacity. The absorbency under load of the superabsorbent hydrogels was determined by using an absorbency under load tester at various applied pressures. A preliminary swelling and deswelling behaviors of the hydrogels were also studied. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and properties of PVA/PVP hydrogels containing chitosan by radiation

Radiation can induce chemical reactions to modify polymers even when they are in the solid state or at a low temperature. Radiation crosslinking can be easily adjusted by controlling the radiation dose and is reproducible. The finished product contains no residuals of substances required to initiate the chemical crosslinking, which can restrict its application possibilities. In these studies, hydrogels for wound dressing were made from a mixture of chitosan and polyvinyl alcohol (PVA)/poly‐N‐vinylpyrrolidone (PVP) by freezing and thawing, gamma‐ray irradiation, or combined freezing and thawing and gamma‐ray irradiation. The physical properties of the hydrogel, such as gelation, water absorptivity, and gel strength, were examined to evaluate the usefulness of the hydrogels for wound dressing. The PVA/PVP composition was 60:40, PVA/PVP–chitosan ratio was in the range 9:1–7:3, and the concentration of, PVA/PVP–chitosan as a solid was 15 wt %. A mixture of PVA/PVP–chitosan was exposed to gamma irradiation doses of 25, 35, 50, 60 and 70 kGy to evaluate the effect of irradiation dose on the physical properties of hydrogels. Water‐soluble chitosan was used in these experiment. The physical properties of the hydrogels, such as gelation and gel strength, were higher when the combination of freezing and thawing and irradiation were used rather than just freezing and thawing. The PVA/PVP–chitosan composition and irradiation dose had a greater influence on swelling than gel content. Swelling percent increased as the composition of chitosan in PVA/PVP–chitosan increased. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1787–1794, 2002     

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.     

Mechanical characteristics of poly(2‐hydroxyethyl methacrylate) hydrogels crosslinked with various difunctional compounds

Poly(2‐hydroxyethyl methacrylate) hydrogels were prepared in the presence of 30 wt% water using two series of crosslinking agents including divinylic (ethyleneglycol dimethacrylate, 1,4‐butanediol dimethacrylate, 2,3‐dihydroxybutanediol 1,4‐dimethacrylate) and diallylic (1,5‐hexadiene‐3,4‐diol and 1,5‐hexadiene) compounds, over a concentration range between 0.1 and 5 mol%. The resulting polymers were swollen in water to yield homogeneous transparent hydrogels. These hydrogels were characterised in terms of equilibrium swelling in water, tensile properties and compression stress–strain measurements. The influences of the nature and the concentration of crosslinking agent on the swelling behaviour and the mechanical properties of these hydrogels were investigated. The crosslinking efficiency of two representative agents (ethyleneglycol dimethacrylate and 1,5‐hexadiene‐3,4‐diol) was quantified by compression experiments. A much lower crosslinking efficiency (0.013) was observed for 1,5‐hexadiene‐3,4‐diol than for ethyleneglycol dimethacrylate (0.336). It is suggested that the low crosslinking efficiency of diallylic agents is responsible for a trend in properties different from that displayed by the gels crosslinked with dimethacrylates. A comparison was made to the similar effect observed previously in heterogeneous PHEMA hydrogels. © 2001 Society of Chemical Industry     

Dynamic and equilibrium swelling studies: crosslinked pH sensitive methyl methacrylate-co-itaconic acid (MMA-co-IA) hydrogels

In the present work crosslinked methyl methacrylate-co-itaconic acid (MMA-co-IA) hydrogels were prepared by free radical copolymerization of methyl methacrylate (MMA) with itaconic acid (IA) using ethylene glycol dimethacrylate (EGDMA) and N, N methylene bisacrylamide (MBAAm) as crosslinkers and benzoyl peroxide as initiator. Prepared hydrogels were investigated for dynamic and equilibrium swelling studies. For swelling behaviour, effect of pH, monomeric compositions, degree of crosslinking and type of crosslinking agent were investigated. Swelling studies were performed in the USP phosphate buffer solutions of varying pH 1.2, 4.5, 5.5, 6.5 and 7.0. Results showed that swelling increased by increasing IA content in hydrogels structure. This may be due to the presence of more carboxylic groups available for ionization. Swelling was decreased with increase in crosslinking ratio owing to tighter hydrogel structure. Hydrogels were characterized by Fourier transform infrared (FTIR), and scanning electron microscope (SEM). Polymer-solvent interaction parameters (χ) of hydrogels were determined by using Flory–Rehner theory of equilibrium swelling values. The analysis of diffusion mechanism from gels using Peppas model showed that all monomeric compositions and degrees of crosslinking followed Fickian diffusion.     

Swelling and Thermal Characteristics of Genipin Crosslinked Chitosan and Poly(vinyl pyrrolidone) Hydrogels

Summary Chitosan / poly(vinyl pyrrolidone) (PVP) were used to prepare semi-interpenetrating polymeric networks. The hydrogels were crosslinked using genipin, a non-toxic cross-linking agent extracted from the fruits of Gardenia jasminoides Ellis. Swelling properties of these hydrogels were studied in media of different pHs and temperatures. States of water in the swollen hydrogels at 25°C and pH 7 were determined using Differential Scanning Calorimetry (DSC). The swelling behaviour of the hydrogels was found to be dependent on the temperature and the pH of the swelling medium. The total water content in the hydrogels was found to increase with increasing PVP content.     

Synthesis and properties of P(NIPAAm‐co‐AM)/SiO2 hybrid temperature‐sensitive hydrogels

Using N, N′‐methylene bisacrylamide as crosslinking agent and potassium peroxydisulfate as initiator, the temperature‐sensitive hydrogels were prepared with organic monomer N‐isopropylacrylamide (NIPAAm) and acrylic amide and inorganic material ethyl orthosilicate (TEOS). The structure of hybrid hydrogels was represented by scanning electron microscopy and Fourier transform infrared spectroscopy. The volume phase transition temperature (VPTT) of hybrid hydrogels was determined by differential scanning calorimetry thermograms of the swollen hydrogel. The results showed that the VPTT of the hydrogels increased with the increasing of TEOS dosage. When the temperature was lower than VPTT, the hydrogels exhibited excellent temperature sensitivity and kept at a swelling state, but when the temperature was higher than VPTT, the hydrogels deswelled significantly. In addition, the compressive strength of hydrogels was studied, the results showed that hybrid hydrogels had more ideal mechanical properties than organic hydrogels. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013