温度敏感聚(N-异丙基丙烯酰胺-co-甲基丙烯酰氧乙基二甲基辛基溴化铵)水凝胶的溶胀性能研究

由于改变亲水／疏水单体比值、与离子单体共聚心、改变凝胶内部结构等均可不同程度地调整温敏水凝胶的溶胀性能,本研究选择一种既含疏水烷基又含季铵盐正离子型亲水基团的两亲性单体——甲基丙烯酰氧乙基二甲基辛基溴化铵（ADMOAB）,结构如示意图1所示．与N-异丙基丙烯酰胺（NIPAM）聚合,制备了P（NIPAM-co-ADMOAB）共聚水凝胶,以便在引入离子型结构单元的同时,改变凝胶体系中亲水／疏水单体比值,避免单纯增加疏水单体引起的水凝胶溶胀性降低问题,并考察了ADMOAB对水凝胶溶胀性能的影响,对该类水凝胶迄今鲜见相关文献报道．该研究对进一步了解水凝胶的构效关系、探索有效控制溶胀性能的途径具有积极意义．     

手性温敏凝胶Poly(NIPAM-co-AAc-L-Trp)的制备及性能

利用L-色氨酸(L-Trp)为手性源,经酯化、缩合等反应制备手性单体AAc-L-Trp,进而在交联剂N,N’-亚甲基双丙烯酰胺(MBAA)和引发剂偶氮二异丁腈(AIBN)的作用下,与N-异丙基丙烯酰胺(NIPAM)发生自由基共聚制备了一种可用于手性拆分的新型手性温敏水凝胶Poly(NIPAM-co-AAc-L-Trp),其结构经IR确证.通过对其温敏性研究发现,相比于PNIPAM凝胶,疏水性手性单体的引入使Poly(NIPAM-co-AAc-L-Trp)凝胶的温敏性下降,LCST随着手性单体含量的增加而降低.以DL-苯丙氨酸为模型药物对其手性识别和拆分性能进行研究,结果表明,手性温敏凝胶可选择性地吸附D-型对映体,且吸附量随着手性单体含量增加而增加;提高温度(45°C)有利于手性温敏凝胶对DL-苯丙氨酸的拆分.     

可降解光交联聚(醚-酐)凝胶用于难溶性药物增溶的研究

将水难溶性药物吲哚美辛包埋于可降解聚(醚-酐)三维光交联网络凝胶中, 使该凝胶具有较好的溶胀性能. X射线衍射测定结果表明, 药物能以分子或无定形态分布, 贮存2个月后药物仍无形态改变, 溶出实验结果表明, 包载在凝胶中的药物比原料药物具有更快的溶出速率和累积溶出量. 采用该法能提高制剂中药物的物理稳定性, 阻延药物析晶, 有效地用于药物增溶.     

手性温敏凝胶 P(NIPAM-co-NALL)的制备及识别性能

以L-亮氨酸(L-Leu)为手性源, 经酯化和缩合等步骤制备手性单体(NALL), 以该单体为手性识别基团, 在交联剂N,N'-亚甲基双丙烯酰胺和引发剂偶氮二异丁腈的作用下, 与N-异丙基丙烯酰胺(NIPAM)以不同的质量比发生自由基共聚, 制备了一系列新型手性温敏水凝胶P(NIPAM-co-NALL), 其结构经红外光谱确证. 相比于PNIPAM水凝胶, 疏水性单体NALL的引入使 P(NIPAM-co-NALL)凝胶的温敏性下降. 以D, L-苯丙氨酸为模型药物对P(NIPAM-co-NALL)凝胶的手性识别和拆分性能进行研究, 结果表明, 手性温敏凝胶对D型对映体具有选择吸附性, 且吸附量随着手性单体含量的增加而增加; 提高温度(40 ℃)有利于手性温敏凝胶对D, L-苯丙氨酸的手性识别和拆分. P(NIPAM-co-NALL)凝胶在重复使用后依然具有手性识别性能, 但其吸附量随着使用次数的增加而下降, 3次重复使用后吸附量下降到原来的27.6%.     

含金刚烷基的N-异丙基丙烯酰胺共聚物水凝胶的制备和性能研究

合成了含金刚烷基的甲基丙烯酸金刚烷酯(AdMA)疏水单体,并通过与N-异丙基丙烯酰胺(NIPAM)共聚,制备了温敏性的(P(NIPAM-co-AdMA))共聚物水凝胶.用傅里叶变换红外光谱仪(FTIR)表征了凝胶的化学结构,用环境扫描电镜(ESEM)对凝胶断层结构的形貌进行了观察,用DSC测试了凝胶的体积相转变温度(LCST),并研究了共聚水凝胶的溶胀性能.结果表明,共聚物水凝胶的LCST能够高效地通过改变疏水单体的含量来调节,在实验所考察的范围内,LCST随AdMA含量的增加而线性降低;疏水单体的含量对凝胶的孔洞结构和溶胀性能存在一最优值,在最优的单体配比下,水凝胶具有均匀规整的大孔结构和超快的响应速率.如疏水单体含量为3%(AdMA∶NIPAM=3%)的共聚物水凝胶具有如渔网般均匀的多孔结构,当发生去溶胀时,在5min内就可以失去92%的水,不到10min的时间就可以完全达到去溶胀平衡,水保留率在4%以下.     

直链型与支链型疏水缔合水凝胶的机械性能与溶胀行为

以丙烯酰胺(AM)为亲水单体,脂肪醇聚氧乙烯醚丙烯酸酯(AEO-AC-n-m,n为疏水端烷基链碳的数目,m为亲水端PEG链的长度,n,m=13,5;10,5;13,10)为疏水单体,十二烷基硫酸钠(SDS)为表面活性剂,过硫酸钾(KPS)为引发剂,通过胶束聚合制备了3种聚丙烯酰胺-co-脂肪醇聚氧乙烯醚丙烯酸酯(AM-co-AEO-AC)疏水缔合水凝胶.以疏水烷基链为直链的疏水单体AEO-AC-13-5合成的直链型水凝胶的网络结构均匀且强度高,其形态在水中可维持180 d.而以疏水烷基链为支链的疏水单体AEO-AC-10-5与AEO-AC-13-10合成的支链型水凝胶的机械性能较弱,60 d内即溶解于水中.在相同条件下,直链型水凝胶断裂时的最大应力是支链型水凝胶的4~5倍.利用弹性橡胶理论中的新胡克方程计算了直链型和支链型水凝胶的有效交联密度ν0和有效交联点间的分子量Mc.     

温敏水凝胶的新进展

从改变亲水／疏水单体比值、与离子单体共聚、改变水凝胶内部结构、调整凝胶溶胀剂四个方面介绍了合成具有不同临界相转变温度、温度响应速度及溶胀比的温敏水凝胶及此类凝胶在药物控释、分离萃取等方面的应用。     

海藻酸钠的疏水改性及释药性能研究

为了提高对疏水性药物的负载量和缓释作用,将海藻酸钠氧化后与十二胺反应使其进行疏水改性.对改性后聚合物结构进行了表征.研究了聚合物在水溶液及盐溶液中的粘度变化;将聚合物分散于NaCl/CaCl2的混合溶液中制备成凝胶微球,对药物布洛芬进行了包埋释放实验.结果表明,疏水改性后的海藻酸钠粘度增加,其凝胶微球对布洛芬负载量提高,具有较好的缓释作用.     

体积相转变温度可调的温敏性N-异丙基丙烯酰胺共聚物微凝胶的制备与性能研究

选用甲基丙烯酸异丙酯(iPMA)与N-异丙基丙烯酰胺(NIPAM)共聚,制备了一系列疏水改性、相转变温度可调的温敏性P(NIPAM-co-iPMA)微凝胶.利用透射电子显微技术(TEM)、浊度法、动态光散射(DLS)技术及示差扫描量热(DSC)技术对所得微凝胶的形态及去溶胀行为进行了表征.TEM与DLS结果表明,所制备的微凝胶具有规则的球型形态.浊度、DLS及DSC结果表明,疏水性单体iPMA的引入能有效调节共聚物微凝胶的相转变温度;在所考察的范围内,微凝胶的相转变温度随iPMA投料比的增加几乎呈线性降低.     

纤维素基智能凝胶的制备、结构及性能研究

纤维素是自然界中最丰富的生物质资源,因其具有可再生性、生物相容性、无毒、可降解等诸多特性,纤维素及其衍生物不仅广泛应用于传统的工业领域,而且在药物控释、组织工程、可穿戴设备材料等领域也有着广阔的应用前景。受到工程技术应用需求的驱动,以纤维素及其衍生物为基材的智能凝胶材料已成为目前的研究热点。作者系统研究了纤维素基智能凝胶材料的制备、结构及性能。主要内容如下： 1.制备了纤维素基气凝胶并对其进行疏水改性,研究了疏水改性后的纤维素气凝胶材料在水下吸附气体的能力,并设计了纤维素基智能捕集器,用于连续不断地吸附从海底释放的甲烷气体。 2.制备了TEMPO氧化的纳米纤维素纤维,并将其用于增强聚丙烯酰胺/明胶形状记忆水凝胶的力学性能;制备的复合水凝胶展示了较好的形状记忆行为,并且该水凝胶的形状记忆性能具有较好的可重复性。 3.利用羧甲基纤维素制备了对多种金属阳离子响应的形状记忆水凝胶;能够通过改变羧甲基纤维素与金属离子之间的交联密度,调节该水凝胶的力学性能。 4.将羧甲基纤维素钠与聚丙烯酸（PAA）复合制备出具有较优异机械性能和自修复性能的聚丙烯酸/羧甲基纤维素钠水凝胶。通过简单的浸泡法,将该复合水凝胶浸泡在氯化钠（NaCl）溶液中,可以促进CMC和PAA之间的链缠结,进一步提升其机械性能。此外,由于水凝胶的导离子性,制备的水凝胶具有良好的传导性能,有望实现在电子皮肤或可穿戴设备中的应用。     

Tunable Amphiphilic Poly(Ether-Anhydride) Gel Nanoparticles for the Delivery of Hydrophobic Drugs

Summary: Biodegradable amphiphilic poly(ether-anhydride) gel nanoparticles (GNPs) with a hydrophobic crosslinked core and a hydrophilic PEG shell have been prepared from amphiphilic photo-crosslinkable ether-anhydride macromers via microemulsion photo-polymerization. The properties of the GNPs, such as degradability, size and drug-loading capacity, were investigated by tailoring the length of PEG chains in macromers from 400 to 4000 and by the addition of a hydrophobic photo-crosslinkable monomer: stearic monoacrylic anhydride (MSA). TEM showed that the GNPs were spherical in shape with a core-shell structure when MSA was added. The GNPs were used as the carriers to enhance the solubility of hydrophobic drugs. Indomethacin (IND) as a model drug was entrapped in the hydrophobic crosslinked core by an in situ embedding method. Results showed that IND maintained chemically intact during the formulation process, and its dissolution rate were improved compared to those of the pure IND. The GNPs prepared from PEG macromer (molecular weight: 4000) with the addition of MSA exhibited the zero-order release behavior, which is potentially useful to control the release of hydrophobic drugs.     

Synthesis of Hydrophobically Modified Poly（acrylic acid） gels and Interaction of the gels with Cationic／Anionic Surfactants

Poly(acrylic acid)(PAA) gel network with only chemical crosslinking and hydorophobically modified PAA(HM-PAA)gels with both chemical and physical crosslinking were synthesized by radical polymerization in tert-butanol,using ethylene glycol dimethacrylate (EGDMA) as crossliker,and 2-(N-ethylperfluorooctanesulfoamido)ethyl methacrylate (FMA),stearyl acrylate (SA) or lauryl acrylate (LA) as Hydrophobic comonomer respectively.The effcet of the fractions and the species of the hydrophobes on swelling properties of HM-PAA gels and the interaction of gels and surfactants were studied.The results showed that the swelling ratio of HM-PAA gels exhibited a sharp decrease with increasing hydrophobic comomomer comcentration,Which Could be sacribed to the formation of strong hydrophobic association among hydrophobic groups.It was proved that two kinds of binding mechanisms of surfactan/gel and different kinds of hydrophobic clusters existed in gels containing both physical and chemical networks.     

热分析技术研究疏水缔合微区对含氟丙烯酸酯共聚物凝胶中水状态的影响

丙烯酸 (AA)与不同含量的 2 (N 乙基全氟辛烷基磺酰胺 )乙基甲基丙烯酸酯 (FMA)在叔丁醇中进行自由基共聚 ,合成了一系列疏水改性共聚物凝胶 .用示差扫描量热法 (DSC) ,热失重分析 (TGA)研究了含氟疏水改性凝胶中水的状态 ,证明FMA改性凝胶中存在 3种状态的水 ,即不可冻结水 ,可冻结结合水和自由水 .对于未改性凝胶和FMA含量为 1mol%的疏水改性凝胶 ,在凝胶中水含量分别低于 0 60 9mol%和 0 698mol%时 ,DSC升温曲线上观察不到熔融峰 ,说明凝胶中存在不可冻结水 .提出计算凝胶中 3种状态的水含量和熔融焓的理论假设 .计算出FMA含量为 1mol%的疏水改性凝胶中自由水和可冻结结合水的摩尔熔融焓分别为75 89 0 3和 6864 0 6J mol.计算结果表明疏水改性后 ,单位聚合物单元上结合的可冻结水数目 (n1 )和非冻结水的数目 (n0 )都增加     

Thermosensitive hydrogel coatings: Synthesis and heparin release

The synthesis and drug release properties of crosslinked N-isopropylacrylamide (NiPAAm) copolymer coatings on the surface of a hydrophobic poly(ester-urethane) tubing were examined. A method was designed to coat hydrophobic polymer surface with a thermosensitive gel layer. Crosslinked NiPAAm copolymer coatings were synthesized using UV-initiated polymerization. The feasibility of using NiPAAm based gels as heparin releasing thermosensitive coatings was investigated. Heparin, a high molecular weight hydrophilic solute, was loaded into hydrogels using a simple solution sorption technique. The release of heparin from NiPAAm copolymer gel coatings was compared to that of crosslinked NiPAAm copolymers. The gel coatings demonstrated a more gradual and prolonged heparin release as compared to gel disks of the same composition.     

Effects of chemical modifications on the swelling behaviors of poly (4-vinyl phenol) gel

Poly (4-vinyl phenol) (P4VPh) gels were prepared by crosslinking with a hydrophilic crosslinker [ethyleneglycoldiglycidylether (EGDGE)] and a hydrophobic one [diglycidyl 1,2-cyclohexane dicarboxylate (DGCHDC)], and the former gel was further modified by CH₃I or C₂H₅I to partially convert the hydrogen of phenol OH to the corresponding alkyl groups. Swelling behaviors of P4VPh gels, thus modified, were investigated to see how the hydrophobic groups introduced to the crosslinker and the polymer substrate affect the super salt resistivity to inorganic ions and the high water content (>90%) that have been observed for the original P4VPh gel. Water content and salt resistivity were unexpectedly preserved even for the modified gels. Effects of the chemical modifications on the gel swelling were only observed in the presence of hydrophobic solutes, i.e., tetrabutyl ammonium chloride and ionic surfactants. All these results strongly suggest that hydration around the polymer substrate in the gel phase is specifically stabilized, probably because of the coexistence of the hydrophobic hydration and the π-hydrogen-bonding hydration around the phenol ring.     

Kinetics of the volume phase transition in poly(n‐isopropylacrylamide) gels prepared under high pressure

New poly(N‐isopropylacrylamide) gels were prepared under high pressure (ca. 200 MPa) during gelation. The preparation‐pressure dependence of the deswelling speed of the gels was measured with a conventional T‐jump method. The deswelling time of a gel rod 2.2 mm in diameter prepared at 193 MPa was about 200 s, 1000 times faster than that of a homogeneous poly(N‐isopropylacrylamide) gel. Moreover, the collective diffusion coefficient, the thermal fluctuation, and the ensemble‐average intensity of the swollen gel networks were obtained with dynamic light scattering measurements. Both the enthalpy and entropy of the gels were estimated from equilibrium swelling curves with the Flory–Huggins interaction parameter evaluated with mean field theory based on the Flory‐type of the Gibbs free‐energy formula. It was found that the networks of the gels had an inhomogeneous structure newly introduced by the preparation pressure. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2315–2325, 2001     

Hard and Soft Capsules: From Branched Polymers to Controlled Release via Gels

Summary: Supramolecular gels, made from the combination of telechelic poly (ethyleneglycols) (PEG's) and trivalent poly(isobutylenes) with terminal matching hydrogen bonds were prepared and their rheological properties were investigated. Addition of poly(N-isopropylacrylamide) as thermosensitive polymer was included into the gel-capsules in amounts of 10 w%, producing gels with strongly thermally- responsive properties. Additionally, dansyl-dyes with two different endgroups (either an hydrophobic endgroup or a multiple hydrogen bond) were encapsulated into the gels as mimicks for pharmaceutically active substances. Monitoring their diffusion by UV-dependent measurements allowed to tune the diffusion and thus the release properties of the gel. The generated supramolecular gels will allow the selective encapsulation and triggered release of various pharmaceuticals and biologically active targets.     

Synthesis and Viscoelastic Properties of Hydrophobically Modified Hydrogels

Summary: We report the synthesis and characterization of a family of hydrophobically modified hydrogels designed to have an improved fracture resistance. A backbone of poly(acrylic acid) (PAA) was functionalized with double bonds and hydrophobic groups. The functionalized PAA was then crosslinked with a dithiol. The chemical structure of the gels was characterized with a combination of NMR, titration methods and rheological techniques. The crosslinked structure of the hydrogel was found to be dependent on the polymer concentration only, while the dissipative properties of the gel increased strongly at all frequencies, with the introduction of hydrophobic groups which formed reversible associations. We expect these viscoelastic hydrogels to display dramatically different properties from the unmodified hydrogels when stretched and fractured.     

Supramolecular structures and conformational transitions in polyelectrolyte gels

Three actual problems connected with the collapse transition of polyelectrolyte gels in poor solvent are reviewed. (i) The first topic is the appearance of microstructures for polyelectrolyte gels in poor enough solvents. Three reasons for microsegregation are discussed: effect of polyelectrolyte – hydrophobic competition, effect of the formation of multiplets from ionic pairs in the ionomer regime and the effect of partial formation of glassy kinetically frozen polymer rich regions. (ii) Second we analyze the interaction of the gels with polymers which are capable to form complexes with the gel chains. Main experimental results are presented for poly(methacrylic acid) gels interacting with poly(ethylene oxide), (iii) Finally, we consider the problem of interaction of polyelectrolyte gels with the sufactants. The micelle formation of surfactants inside the gel and its consequences for the conformational properties of the gel are discussed in detail.