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Synthesis and Properties of Two Types Weak Hydrogels Based on Hydrogen Bonds

Author: LiuBoTian
Tutor: JiangZhenHua
School: Jilin University
Course: Polymer Chemistry and Physics
Keywords: hydrogels hydrogen bonds P(AA-co-AAm) environmentally response
CLC: O648.17
Type: Master's thesis
Year: 2012
Downloads: 55
Quote: 0
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Abstract


Hydrogels can be divided into chemical hydrogels and physical hydrogels,according to their ways of bonding networks. As for physical hydrogels, their networkstructures are formed by intermolecular interaction, including hydrophobic associateddomains and hydrogen bonds. Copolymers of acrylic acid (AA) and acrylamide (AAm)can form a weak hydrogel through the hydrogen bonds between amide and carboxylgroups. Above a certain temperature, it becomes sol due to the dissociation of hydrogenbonds, which macroscopically shows the transition from heterogeneous opaque tohomogeneous transparency. In the first part of this study, a small amount of MPEG-AC(methoxy poly(ethylene glycol) acrylite) and SDS were introduced into thecopolymerization systems of AA and AAm, and weak hydrogels with sable volume basedon hydrogen bonds were prepared by free radical copolymerization in aqueous solution.The effects of MPEG-AC content, SDS content, and MPEG side chain length on the phasetransition behaviors driven by temperature were discussed in detail. The results showed:(a)The transition temperature of the hydrogels decreased with the increasing of MPEG-ACcontent and MPEG-AC chain length, which caused by the adulterating effect ofMPEG-AC.(b) Since the dissociated micelles formed by SDS added the exclusive volumeof the motion of copolymer chains, the transition temperature of the hydrogels increasedwith the increasing of SDS content.(c) There was interaction between SDS and MPEGside chains, which weakened the both of adulterating effect and additional exclusivevolume effect.It is expected that the micro-hydrogels with core/shell structure can be constructed byneans of combining the surface-modified latex particles and other water soluble polymerswhich can strongly interact with the groups on the particle surface, in which the latexparticle acts as core and the polymer as shell. In the second part of this study, P(St-4VP) core-shell microspheres were synthesized via a method of one-stage soap-free emulsioncopolymerization of styrene (St) and4-vinylpyridine (4VP). The effects of formulationand technology on the mean diameter of the latex particles and their dispersivity weredetailed dicussed. The results showed that the mean hydrodynamic diameter of P(St-4VP)microspheres could be effectively adjusted from420nm to640nm by changing formulasand technology besides a narrow distribution of their sizes were achieved. In the basis ofcombination between a kind of P(St-4VP) latex and poly(acrylic acid) or acrylicacid/acrylamide (1/1mol) copolymer solutions, functional microgels with thermal and pHsensibility could be expediently obtained.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Colloid chemistry ( physical and chemical dispersion system ) > Colloid > Gel and soft
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