The materials had the ability to collapse from a fully swollen conformation in less than 20 minutes
Gel without graft chain required up to a month to fully collapse
MD5
hydrogels obtained at different pH values.
MD3
MD4
pH = 9.5
MD6
MD7
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凝胶的性质
（1）触变性：物理凝胶受外力作用，网状结构被破 坏而变成流体，外部作用停止后，又恢复成半固体 凝胶结构，这种凝胶与溶胶相互转化的过程，称为 触变性。 （2）溶胀性：指凝胶吸收流体后自身体积明显增大 的现象，是弹性凝胶的重要特性。 （3）脱水收缩性：溶胀的凝胶在低蒸气压下保存， 流体缓慢地自动从凝胶中分离出来的现象。 （4）透过性：凝胶与流体性质相似，可以作为扩散 介质。
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content
凝胶的定义 凝胶的分类 凝胶的制备 凝胶的应用
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凝胶：
指溶胀的三维网状结构高分子，即聚合物分子间相互 连结，形成空间网状结构，而在网状结构的孔隙中又 填充了液体介质。由于液体与高分子网络的亲和性， 液体被高分子网络封闭在里面，失去了流动性，因此 凝胶能象固体一样显示出一定的形状。
聚(N-异丙基丙烯酰胺) PNIPAAm
O = Susceptive to hydrolysis
poly(ethylene g lycol)
聚氧乙烯
poly(vinyl alcohol)聚乙烯醇 poly(N-vinyl-2-pyrrolidone)聚(N-乙烯基-2-吡咯烷酮)
(PNVP) poly(ethylene glycol)聚乙二醇 poly(hydroxyethyl metharylate) 聚甲基丙烯酸羟乙酯
CH3
HO
CH2
CH2
O x CH2
C H
O y CH2 CH2 O x H
Poly(ethylene oxide-co-propylene oxide-co-ethylene oxide) (PEO-PPO-PEO)
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Applications of Hydrogels in Drug Delivery
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Applications of Hydrogels in Drug Delivery
Environment-Sensitive Hydrogels
• respond to environmental change : temperature, pH, specific molecule
• reversible volume phase transition or sol-gel phase transition
高分子凝胶
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• gel 凝胶 • hydrogel 水凝胶 • soft & wet matter 软湿件 • intelligent or smart material 智能/灵巧材料 • fuzzy 模糊
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海参有一个特性：如 果有谁用手去碰一下它 柔软的身体，它就会一 下变得象木头一样坚硬， 但如果将它在手中紧捏 一会，它就会慢慢地溶 变成滑溜溜的液体从你 手中逃走。
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互穿聚合物网络( interpenetrating polymer network, IPN)
由两种或两种以上聚合物通过网络互穿缠结而形成的一 类独特的聚合物共混物或聚合物合金。 IPN特有的强迫作用 能使两种性能差异很大或具有不同功能的聚合物形成稳定的 结合，从而实现组分之间性能的互补。同时IPN的特殊细胞状 结构、界面互穿、双相连续等结构形态特征，又使得它们在 性能或功能上产生特殊的协同作用，防止相分离，并极大地 提高了水凝胶的机械强度，并可以提高它的响应性。
Poly(N-isopropyl acrylamide)聚异丙基丙烯酰胺 (PNIPAAm) LCST (lowest critical solution temp): 34.30C
Below LCST: significant gel swelling occurred, Transition about this point as reversible LCST raised when PNIPAAm copolymer with
H
CH2 C n
CO
NH
H CH2 C
C
CH3
CH2
CH
n
O
CO
NH
O
CH
H3C
CH3
CH
CH2CH2CH2CH3
H3C
CH3
Poly(N-isopropylacrylamide) (PNIPAAm) Poly(NIPAAm-co-butyl methacrylate) P(NIPAAm-co-BMA)
A polymer gel is a threedimensional network swollen by a large amount of solvent. It has some properties between solutions and solids.
MD2
SEM micrograph of pHsensitive copolymer P(DEAM-co-MAA)
• ionic interaction, hydrogen bonding, antigen-antibody interaction, supramolecular association
• Ionic hydrogel
Chemical and Physical crosslinking
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DNA水凝胶，无须交联剂
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Temperature-sensitive hydrogels
poly(N-isopropylacrylamide) and its copolymers nylon capsule grafted poly(IPAAm)
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Temperature-sensitive hydrogels
Major promise for rapid and abrupt or oscillatory release of drugs, peptides, or proteins
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pH敏感性
离子强度敏感性
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高分子凝胶的制备
起始原料： 单体(水溶或油溶单体) 聚合物(天然或合成聚合物) 单体和聚合物的混合物
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Bonding in hydrogels •Covalent •Ionic •Hydrogen bonding •Polypeptide complexation(e.g., coiled coils) •Hydrophobiceffect
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7
MD2
MD3
MD4
pH = 7.0
MD5
MD6
MD7
• Molecular structures of environmental-sensitive hydrogels
(2) pH sensitive hydrogel
H
CH2 C n
COOH
H
CH2 C n
CO O CH2CH2N(CH2CH3)2
两个前提: 主链或侧链上带有大量的亲水基团 适当的交联网络结构
制备方法： 单体的交联聚合 接枝共聚 其它交联或转化等
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高分子凝胶的制备
Chemical crosslinking Polymerization of water soluble monomers in the presence of bi- or multifunctional cross-linking agent
Drug release by the squeezing acti2o6n
药物释放曲线
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Applications of Hydrogels in Drug Delivery
• Molecular structures of environmental-sensitive hydrogels
(1) Temperature sensitive hydrogel
pH响应性凝胶 温度响应性凝胶 光响应性凝胶 电场响应性凝胶 盐敏凝胶 压力敏感性凝胶
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pH- sensitive hydrogels
含有羟基或胺基
Most common ionic polymers: poly(acrylamide) PAAm, poly(acrylic acid)聚丙 烯酸 (PAA), poly(methacrylic acid) (PMAA)聚 甲基丙烯酸 , poly(diethylaminoethyl methacrylate)二乙基胺基乙基甲基丙烯酸酯 (PDEAEMA), and poly(dimethylaminoethyl methacrylate) (PDMAEMA)
small amount of ionic monomers Heterogeneous gels containing PNIAAm
collapsed at significantly faster rate than homopolymer of PNIPAAm
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Temperature-sensitive hydrogels
+
Copolymerization Monomer Crosslinker
Polymerization
Hydrogel network
Vinyl group-containing water-soluble polymers