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Effect Of Surfactants On Self-assembly Behaviors Of HPAM In Aqueous Solution

Posted on:2013-02-25Degree:MasterType:Thesis
Country:ChinaCandidate:P P PangFull Text:PDF
GTID:2211330371464580Subject:Applied Chemistry
Abstract/Summary:PDF Full Text Request
Low-molecular-weight polyacrylamide (PAM) was prepared by the solution polymerization. And the partially hydrolyzed polyacryamide (HPAM) with different hydrolyzing degree (HD) were obtained via a hydrolysis reaction. First, the self-assembly behaviors of HPAM in pure aqueous solution in pH response and the self-assembly mechanism were investigated. Then the effects of ionic surfactants on the morphologies of polymeric aggregates were also researched in this work.The structures of the polymeric aggregates were characterized by Transmission electron microscopy (TEM), dynamic laser light scattering (DLS), zeta potential and TEM of in-situ reduction sedimentary of HAuCl4 on self-assemblies. The results showed that HPAM self-assembled into spherical aggregates (D=150 nm) at pH 2.5. Flake polygon self-assemblies (450×250×50 nm) were obtained at pH 1.3, and TEM characterization after in-situ reduction sedimentary of HAuCl4 revealed that the flake polygon self-assemblies were multivesicular vesicles with the delicacy structure of hydrophilic inner vesicle @ hydrophobic continuous cyst wall @ hydrophilic shell. When pH decreased to 0.9, the flake polygon self-assemblies disappeared and the uniform spherical colloidal particles with diameter of 10 nm were observed by TEM after in-situ reduction sedimentary of HAuCl4. Conversely, HPAM self-assembled into spherical aggregates (D=200 nm) when pH increased to 12.5. And when the HD of HPAM lower than 40%, multivesicular vesicles (500×250×50 nm) were generated, but when HD higher than 40%, HPAM self-assembled into string beads-like or cube-like aggregates.The effects of cetyl trimethyl ammonium bromide (CTAB) or sodium dodecyl sulfate (SDS) on the polymeric self-assembly behaviors were explored. The results showed that the morphologies of the self-assemblies related to the types, concentration and addition methods of surfactants. At pH 1.3, when CTAB was added into system before acid, the morphologies of the self-assemblies changed from short rod-like aggregates (100 nm) to the flake polygon multivesicular vesicles and then into flower cluster aggregates with the concentration of CTAB increasing. When CTAB was added into system with acid, HPAM self-assembled into the flake polygon multivesicular vesicles at low concentration and rod-like aggregates (350 nm) at high concentration. However, when SDS was added into system before acid, with the concentration of SDS increasing, the HPAM aggregates changed from short rod-like to coagulated spherical aggregates (D=100 nm). When SDS was added into system with acid, spherical aggregates were obtained. Moreover, the range of pH formed regular self-assemblies enlarged after surfactant added.
Keywords/Search Tags:olymeric self-assembly, random copolymers, partially hydrolyzed polyacrylamide, pH-induced, multivesicular vesicles, HAuCl4, in-situ reduction, surfactants
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