The Studies On The Sol-gel Phase Transition Of Thermosensitive Nanogel Binary Assemblies Using Electrostatic Interaction

Molecule assembling technique plays a great role in construction of new functionalmaterial. Nanoparticles can regulate self-structure between ordered and unordered bymolecule assembling. Such as nanogel gelation, it happens in the system which is filledwith attraction broadly. Especially particle systems with strong short-range attractive force,they can form a three-dimensional gel with fractal structure by the dynamic mechanism ofDiffusion-Limited Cluster Aggregation （DLCA）. Such short-range force includeselectrostatic attraction, multiple hydrogen bond, hydrophobic interaction et al.This paper aims to design several thermosensitive nanogels with different electriccharge by Seed emulsion polymerization, study their nano-characters, the impact onassembling and microscopic fractal structure from the temperature/pH dependence ofintermolecular force strength and scale, and discuss their drug loading and releasinginitially. The detail work and some results are as follows:1) Research on binary nanogel assembly of poly （poly （ethyl glycol） ethyl ethermethacrylate-co-2-（Diethylamino）ethyl methacrylate）（PMD） and poly（N-Isopropylacrylamide-co-Acrylic acid）（PNA）, the former is a positive charged nanogelwith core-shell structure and the later negative one:â‘ Optimization of the synthesis ofPMD. The optimum in150mL system is MEO₂MA:7.0mmol,1.69mL, PEG-750:0.27mmol,200mg, V-50:0.028mmol,7.5mg, CTAB:0.015mmol,5.6mg, DEA:0.6mmol,0.120mLâ‘¡the quantity of PEG-750, CTAB and V-50have impact on stabilityof pMEO₂MA. More PEG-750, bigger size of pMEO₂MA, more CTAB and V-50, smallersize of pMEO₂MA. When quantities of them reach a certain degree, size of PMD becomesstable.â‘¢The effect of temperature on size and Zeta potential of PMD. It showsdifference of temperature dependence between NIPAM and MEO₂MA.â‘£Phasetransition of binary nanogel assemblies PNA:PND. Only10wt%PMD and PNA can gelate;mixture ratio doesn’t have effect; The addition of acid improves phase separation ofnanogel and water; NaCl promotes gelation of binary nanogels.⑤Rheological behaviorof PNA:PMD assembly. Result of rheological properties demonstrates that binary nanogel PNA:PMD can’t gelate.2) Research on binary nanogel assembly of poly （N-Isopropylacrylamid-co-2-（Diethylamino）ethyl methacrylate）（PND） and PNA, the former is a positive chargednanogel with core-shell structure:â‘ The effect of temperature and pH on size and Zetapotential of PND and PNA.â‘¡The effect of mixing ratio, temperature, pH and saltconcentration on binary nanogel assemblies. The sample of PNA:PND=1:7is larger thanothers at room temperature. This value is equal to the absolute one of-13.1mV/+2.25mV,which are Zeta potentials of PNA and PND respectively. When pH<4.0or>8.0, assemblysize is larger at high temperature. As a result of protonation and deprotonation, PNA andPND have the same charged surface, which leads to interparticle electrostatic repulsion.NaCl lowers VPTT of binary nanogel by destroying hydrated sheath and ionic layer on theparticle surface, which makes nanogel unstable at high temperature.â‘¢Molar weight ofcharged groups on the surface of PNA and PND nanogels. Molar weight of Chargedgroups of PNA and PND are7.698×10-3mmol and1.955×10-3mmol respectively, whichratio is about4:1.â‘£Phase transition of PNA:PND assembly. Lowest critical gelationtemperature of PNA:PND is2wt%, ST reduces as growth of nanogel concentration.Samples with mixing ratio PNA:PND=1:7/1:9/1:11/1:15have lower ST. pH has nodifference on phase transition. Addition of NaCl promotes gelation of binary nanogel.⑤Rheological behavior of PNA:PND assembly. Results of this part confirm the formerexperience quantitively, it also makes a conclusion that sample of PNA:PND=1:11at pH7has the best rheology properties.