聚甲基丙烯酸N,N-二甲基氨基乙酯水凝胶敏感性研究

采用热化学聚合法制备了聚甲基丙烯酸N,N-二甲基氨基乙酯(PDMAEMA)水凝胶,对其溶胀性能进行了研究,考察了温度、pH和离子强度对其溶胀行为的影响.结果表明,PDMAEMA水凝胶具有温度敏感性,其低临界相变温度在50℃左右;水凝胶具有pH敏感性,其溶胀率在pH=8附近有一突变的下降过程;具有离子强度敏感性,溶胀率随离子强度的增加呈线性下降的趋势.     

pH-温度双重敏感性水凝胶的制备及溶胀性能研究

制备具有pH及温度双重敏感性水凝胶。通过自由基聚合反应制备出NIPAM-co-PMAA水凝胶材料。考察不同单体甲基丙烯酸(MAA)和N-异丙基丙烯酰胺(NIPA)配比对pH和温度的响应能力,探究其溶胀性能。结果表明,不同配比的水凝胶具有双重敏感性。NIPA含量不同时,对于LSCT温度有影响,MAA含量不同时,在酸性条件下溶胀率较大。结论,NIPAM-co-PMAA水凝胶有望成为药物载体。     

甲基丙烯酸β-羟乙酯共聚水凝胶的合成及性能研究

以HEMA、AAM为共聚单体,采用溶液聚合法合成了HEMA/AAM共聚水凝胶,并对其溶胀动力学、离子强度、温度、pH值等性能进行了测定。实验表明:合成的水凝胶初始溶胀迅速,达到平衡溶胀比平衡约6h;在不同离子强度的水溶液中,随着离子强度I的增大,凝胶的ESR不断降低;在pH<7时,其EKR随pH值的增加而减少,在pH>7时,其ESR随pH值的增加而猛增,因为发生了水解反应;凝胶的ESR随温度的升高而降低。     

温度与pH敏感性大孔聚P（NIPAM-co-MAA）水凝胶的制备及性能研究

以乙醇水溶液作为反应介质,成功制备了温度与p H快速响应性聚（N-异丙基丙烯酰胺-co-甲基丙烯酸）[P（NIPAM-co-MAA）]水凝胶,研究了乙醇水溶液的浓度对凝胶性能的影响。通过红外光谱（FT-IR）﹑扫描电镜（SEM）﹑测溶胀比对凝胶性能进行了表征。结果表明,凝胶具有相同的化学组成与结构,但具有不同的微观形态;当乙醇浓度为30%-80%时,凝胶的溶胀率和退涨率随着反应介质中乙醇浓度的增加而增加。所制备的凝胶表现出较强的温度与p H敏感性以及较快的去溶胀速率。     

聚甲基丙烯酸/丙烯酰胺pH敏感凝胶的合成与溶胀行为研究

以单体丙烯酰胺(AM)、甲基丙烯酸(MAA),交联剂N-N'亚甲基双丙酰胺(BIS)为原料,通过自由基共聚合成了聚甲基丙烯酸/丙烯酰胺[P(MAA-co-AM)]水凝胶.研究了干凝胶在不同pH溶液中的溶胀动力学,结果表明不同AM、MAA单体配比的凝胶溶胀性具有很大差异,其溶胀率都随着溶液的pH增加而增大,在pH=12和pH=2溶液反复变换时显示可逆溶胀-退溶胀和快速响应特性,溶胀-退溶胀过程中搅拌作用对凝胶响应速率有显著影响.吸水平衡P(MAA-co-AM)水凝胶在酸性及碱性条件下均出现收缩,在pH=2下10 min之内凝胶收缩90%以上,随着pH增大逐渐减慢.通过不同浓度的NaCl与CaCl2溶液研究了溶液离子强度以及反离子的电荷数对凝胶溶胀性影响,在NaCl溶液和水中,呈现反复溶胀-退溶胀响应特性.     

快速响应大孔聚(N-异丙基丙烯酰胺-co-甲基丙烯酸)水凝胶的制备及性能研究

在不同浓度的氯化钠水溶液中,成功制备了聚(N-异丙基丙烯酰胺-co-甲基丙烯酸)[P(NIPAM-co-MAA)]水凝胶,用红外光谱仪(FT-IR)、扫描电镜(SEM)、测溶胀比对凝胶性能进行了表征,讨论了凝胶内部微观结构的形成机理,以及它们对凝胶性能的影响。发现当氯化钠浓度大于0.3 mol·L-1时凝胶内部形成孔洞网络结构,随着其浓度的增加孔洞网络结构越来越明显,同时凝胶表现出较快的响应速率。     

PASP/SPP水凝胶溶胀性能的研究

采用水溶液聚合法制备聚天冬氨酸/沙柳木粉(PASP/SPP)水凝胶,采用傅里叶红外光谱(FTIR)、X射线衍射(XRD)和扫描电镜(SEM)对其结构进行表征。研究了溶胀时间、溶胀温度、溶液pH值、离子强度等对水凝胶溶胀性能的影响。结果表明,FTIR和XRD显示PASP上的—COOR与沙柳木粉上的O—H发生接枝共聚反应,并形成PASP/SPP水凝胶;SEM显示其表面疏松,有大小不等的孔隙,有利于提高水凝胶的溶胀性能。当溶胀时间为60 min、溶胀温度为30℃、溶液pH值为5.5、离子强度为0时,PASP/SPP水凝胶的溶胀比达到最大,为7.2。     

PASP/SPP水凝胶溶胀性能的研究

采用水溶液聚合法制备聚天冬氨酸/沙柳木粉(PASP/SPP)水凝胶,采用傅里叶红外光谱(FTIR)、X射线衍射(XRD)和扫描电镜(SEM)对其结构进行表征。研究了溶胀时间、溶胀温度、溶液pH值、离子强度等对水凝胶溶胀性能的影响。结果表明,FTIR和XRD显示PASP上的—COOR与沙柳木粉上的O—H发生接枝共聚反应,并形成PASP/SPP水凝胶;SEM显示其表面疏松,有大小不等的孔隙,有利于提高水凝胶的溶胀性能。当溶胀时间为60 min、溶胀温度为30℃、溶液pH值为5.5、离子强度为0时,PASP/SPP水凝胶的溶胀比达到最大,为7.2。     

温度和pH值对智能水凝胶溶胀行为的影响

以N-马来酰化壳聚糖(N-MACH)为交联剂,N-异丙基丙烯酰胺(NIPAAm)为单体,羧甲基纤维素钠(CMC)为半互穿材料,分别合成了PNIPAAm和PNIPAAm/CMC半互穿网络智能水凝胶,研究了两种水凝胶在不同温度的去离子水和不同pH值的缓冲溶液中的溶胀现象,结果表明介质温度和pH值对水凝胶的溶胀行为有显著影响。在温度和pH值一定时,水凝胶的溶胀率随着交联剂用量的增加而下降,随着CMC用量的增加而上升。     

AM与HEMA共聚制备水凝胶接触镜材料及其溶胀性能

采用丙烯酰胺(AM)与甲基丙烯酸β-羟乙酯(HEMA)进行本体共聚制备水凝胶接触镜材料,研究了水凝胶的溶胀性能及其温度和pH值敏感性。结果表明,引发剂过氧化苯甲酰(BPO)用量为反应单体总质量的0.3%、反应温度80℃,产物溶胀之后为无色透明的玻璃状水凝胶;共聚物水凝胶具有较好的pH值敏感性,水凝胶在酸性溶液中溶胀,在碱性溶液中收缩:含有AM的水凝胶,其pH值敏感性较大:随AM的含量增大,共聚物水凝胶的溶胀速度和饱和含水量增大,随温度升高,水凝胶的饱和含水量下降,共聚物水凝胶中AM的含量对其温度敏感性无显著影响:SEM照片显示,AM与HEMA共聚物存在均匀的纤维状结构,并且共聚物中AM的含量越大,这种纤维状结构越大、越明显。     

Swelling behaviour of a new kind of polyampholyte hydrogel composed of dimethylaminoethyl methacrylate and acrylic acid

Poly[(dimethylaminoethyl methacrylate)‐co‐(acrylic acid)] [poly(DMAEMA‐co‐AAc)] hydrogels have been synthesized by UV‐induced copolymerization of dimethylaminoethyl methacrylate (DMAEMA) and acrylic acid monomer. The effects of pH and ionic strength on the swelling behaviour of poly(DMAEMA‐co‐AAc) hydrogels were investigated in detail. It was found that there is minimal equilibrium swelling ratio (ESR) for the hydrogels with the change of pH, and the pH at minimal ESR of the hydrogels was defined by the isoelectric points (IEP), similar to the situation with protein molecules. The IEP of the hydrogels shifted to higher values with increase in the DMAEMA content in the hydrogels. Antipolyelectrolyte behaviour of the hydrogels at a pH near the IEP was observed as well, and the ESR increased with increasing ionic strength. The study of swelling kinetics of the hydrogels showed that the swelling process was Fickian at the IEP and non‐Fickian when the pH deviated from the IEP. Copyright © 2003 Society of Chemical Industry     

Synthesis and characterization of new methacrylate-type hydrogels containing 2-tert-butylamino ethyl groups for sorption purposes

Crosslinked poly[2-(tert-butylamino)ethyl methacrylate] (PtBAEMA) hydrogels were synthesized by ⁶⁰Co-γ-radiation-initiated simultaneous polymerization and crosslinking of 2-(tert-butylamino)ethyl methacrylate in bulk and in aqueous solutions. The results showed that the gelation percentage decreased with increasing water content. The structural and thermal characterizations of the hydrogels were accomplished with several techniques, including Fourier transform infrared spectroscopy, swelling measurements, thermogravimetry, and differential scanning calorimetry. The effects of time, pH, temperature, and ionic strength on the swelling behavior were also investigated. Swelling equilibrium was attained in 2–3 days. PtBAEMA hydrogels originally swelled to 350% (by volume) in deionized water, but this value reached 3000% around pH 2.0. PtBAEMA hydrogels were reversibly affected by the change in temperature within the temperature range of 4–70°C. The swelling ratios of the gels decreased with increasing ionic strength. As a result, PtBAEMA hydrogels show stimuli-responsive properties depending on the characteristics of the environment, and they are being considered for adoption as some kind of carrying material for separation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Swelling behavior of poly(acrylamide‐co‐N‐vinylimidazole) hydrogels under different environment conditions

A series of random copolymers of acrylamide and N‐vinylimidazole, poly(AAm‐co‐NVI), with various compositions were prepared using redox copolymerization. The influence of environmental conditions such as pH, temperature, and ionic strength on the swelling behavior of the copolymeric hydrogels was investigated. The hydrogels exhibited the highest equilibrium swelling in basic medium at high temperature. Equilibrium swelling decreased with rising ionic strength at pH 5.0. As pH increased, equilibrium swelling of the hydrogels increased at pH 11.0 and I = 0.20 M. Swelling kinetics of the hydrogels was found to be non‐Fickian at 25°C. The process tended to be Fickian at higher pH and temperature. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1783–1788, 2005     

Synthesis and characterization of pH- and temperature-sensitive hydrogel of N-isopropylacrylamide/cyclodextrin based copolymer

A reactive β-Cyclodextrin (β-CD) based monomer carrying vinyl carboxylic acid functional groups was synthesized via reaction of β-CD with maleic anhydride (MAH) in N,N-dimethylformamide (DMF) at 80 °C. By copolymerization of the monomer with N-isopropylacrylamide (NIPA), a novel hydrogel, poly(NIPA-co-MAH-β-CD) with pH and temperature sensitivities plus molecular inclusion function, was obtained using free radical polymerization in aqueous solution. The hydrogel's composition was determined by element analysis and infrared spectroscopy. Equilibrium swelling ratio (ESR) of hydrogels was tested under different environment of pH, temperature and ionic strength. The results indicated that ESR of hydrogels presents marked variations following the change of experimental conditions used.     

Synthesis,characterization and,swelling behavior of semi‐IPN nanocomposite hydrogels of alginate with poly(N‐isopropylacrylamide) crosslinked by nanoclay

pH and temperature responsive nanocomposite hydrogels were synthesized with sodium alginate (NaAlg), N‐isopropylacrylamide (NIPA), and nanoclay. The structure, morphology, thermal behavior, and swelling and deswelling behaviors of the hydrogels were studied. The NaAlgm/PNIPA/Clayn hydrogels revealed a highly porous structure in which the pore sizes decreased and the amount of pores increased with increasing the nanoclay content in the hydrogels. PNIPA retained its own characteristics regardless of the amount of NaAlg and nanoclay. The effect of pH and nanoclay content on the swelling and effect of temperature on the deswelling behavior were investigated. The equilibrium swelling ratios of the nanocomposite hydrogels increased with increasing the pH from 2 to 6. The maximum swelling was attained at pH 6. Deswelling increased with increasing the nanoclay content in the hydrogels. The hydrogels were found to be pH and temperature responsive. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43222.     

Gamma radiation synthesis and swelling properties of hydrogels based on poly(ethylene glycol)/methacrylic acid (MAc) mixtures

In this work, gamma radiation was used to prepare hydrophilic hydrogels based on different mass ratios of poly(ethylene glycol) (PEG) and methacrylic acid (MAc) monomer. The thermal stability of hydrogels was characterized thermogravimetric analysis (TGA). The effect of temperature and pH, as external environments, on the equilibrium swelling of PEG/MAc hydrogels was also studied. The results showed that the gel fraction of PEG/MAc hydrogels is lower than that of PMAc hydrogel, in which the gel fraction of PMAc hydrogel was decreased greatly with increasing the mass ratio of PEG polymer in the initial solutions. The results showed that PEG/MAc hydrogels reached the equilibrium swelling state in water after 6 hours. It was found that the equilibrium swelling of PEG/MAc hydrogels displayed a transition change within the temperature range 30–40°C. This change in equilibrium swelling was illustrated by differential scanning calorimetry (DSC). However, it was observed that the equilibrium swelling of PEG/MAc hydrogels increases progressively with increasing the pH value from 4 up to 8. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of hydrogels based on gamma irradiation of acrylic acid and methacrylic acid

In this work, hydrogels based on different ratios of acrylic acid (AAc) and methacrylic acid (MAc) monomers were prepared by gamma radiation copolymerization. The hydrogels were characterized by IR spectroscopy and thermogravimetric analysis (TGA). The effect of temperature and pH on the degree of swelling of AAc/MAc hydrogels was also studied. The results showed that the gel fraction of AAc is relatively higher than MAc, while the gel fraction of AAc/MAc hydrogels decreased slightly with increasing the ratio of MAc monomer in the initial solution. The IR spectroscopic analysis indicates the formation of copolymer networks and the presence of hydrogen bonding. The thermal study showed that PAAc hydrogel displayed higher thermal stability than PMAc and AAc/MAc hydrogels, over the studied compositions. The results showed that PAAc hydrogel reached equilibrium swelling state in water after 4 h, whereas PMAc and AAc/MAc hydrogels reached the equilibrium after 7 h. In this regard, AAc/MAc hydrogels showed degree of swelling in water lower than PAAc and higher than PMAc hydrogels. It was found that the swelling of the hydrogels based on AAc and MAc monomers or their copolymers increases with increasing temperature up to 50°C. Moreover, it was observed that the degree of swelling of hydrogels were not affected by increasing the pH values up to 4 and increased greatly within the pH values from 5 to 9. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Investigation of mechanical and thermodynamic properties of pH‐sensitive poly(N,N‐dimethylaminoethyl methacrylate) hydrogels prepared with different crosslinking agents

pH‐sensitive poly(N,N‐dimethylaminoethyl methacrylate) hydrogels were synthesized by free‐radical crosslinking polymerization using two different crosslinking agents; tetraethylene glycol dimethacrylate (TEGMA) and N,N′‐methylenebis(acrylamide) (BAAm). The influence of the polymerization factors such as the type of the crosslinking agent and the gel preparation concentration on the swelling behavior, the gel strength, the effective crosslinking density and the average chain length between the crosslink points for the resulting hydrogels was investigated. The results of the equilibrium swelling measurements in water showed that the linear swelling ratio of the resulting hydrogels increases with increasing gel preparation concentration. The swelling ratio of PDMAEMA hydrogels crosslinked with BAAm is larger than those for hydrogels crosslinked with TEGMA over the entire range of the polymer network concentration. The hydrogels exhibit very sharp pH‐sensitive phase transition in a very narrow range of pH between 7.7 and 8.0. From the mechanical measurements, it was also found that the linear swelling ratio of resulting hydrogels depends on the crosslinking density and also the type of the crosslinker used in the preparation. The resulting hydrogels are thought to be good candidates for pH‐sensitive drug delivery systems. POLYM. ENG. SCI. 2013. © 2012 Society of Plastics Engineers     

FTIR-ATR measurements of the ionization extent of acrylic acid within copolymerized methacrylated dextran/acrylic acid networks and its relation with pH/salt concentration-induced equilibrium swelling

In this study, dextran hydrogels were obtained by free radical copolymerization of methacrylated dextran with acrylic acid (AAc) in aqueous solution. The fractions of dissociation of AAc units within hydrogel in response to changes in pH and ionic strength of external aqueous solution were determined by FTIR-ATR spectroscopy. The influence of small ion concentration within hydrogel on the dissociation constant of AAc follows the Debye-Hückel behavior. Based on the results from the FTIR-ATR measurements, the total ion concentration difference inside and outside the hydrogel was determined according to the Donnan equilibrium theory, taking account of the counterion condensation effect quantitatively. The swelling response of hydrogels to changes in external pH and ionic strength was governed mainly by the ionic osmotic pressure due to the accumulation of diffusible ions within hydrogels. The energy balance between the osmotic and elastic retractile responses indicates the non-Gaussian behavior of elastically effective subchains with increasing swelling.