Criteria of negative thixotropy of poly(methyl methacrylate) solutions as a function of temperature and of the thermodynamic quality and viscosity of the solvent

1984 ◽  
Vol 262 (3) ◽  
pp. 189-196 ◽  
Author(s):  
P. Bradna ◽  
O. Quadrat
Keyword(s):  
Methyl Methacrylate ◽  
Poly Methyl Methacrylate ◽  
Negative Thixotropy ◽  
Thermodynamic Quality

scholarly journals Self-Assembly of Molecular Brushes with Polyimide Backbone and Amphiphilic Block Copolymer Side Chains in Selective Solvents

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2922
Author(s):  
Maria Simonova ◽  
Ivan Ivanov ◽  
Tamara Meleshko ◽  
Alexey Kopyshev ◽  
Svetlana Santer ◽  
...  
Keyword(s):  
Block Copolymer ◽  
Methyl Methacrylate ◽  
Self Assembly ◽  
Amphiphilic Block Copolymer ◽  
Side Chains ◽  
Poly Methyl Methacrylate ◽  
Molecular Brushes ◽  
Selective Solvents ◽  
Significant Difference ◽  
Thermodynamic Quality

Three-component molecular brushes with a polyimide backbone and amphiphilic block copolymer side chains with different contents of the “inner” hydrophilic (poly(methacrylic acid)) and “outer” hydrophobic (poly(methyl methacrylate)) blocks were synthesized and characterized by molecular hydrodynamics and optics methods in solutions of chloroform, dimethylformamide, tetrahydrofuran and ethanol. The peculiarity of the studied polymers is the amphiphilic structure of the grafted chains. The molar masses of the molecular brushes were determined by static and dynamic light scattering in chloroform in which polymers form molecularly disperse solutions. Spontaneous self-assembly of macromolecules was detected in dimethylformamide, tetrahydrofuran and ethanol. The aggregates size depended on the thermodynamic quality of the solvent as well as on the macromolecular architectural parameters. In dimethylformamide and tetrahydrofuran, the distribution of hydrodynamic radii of aggregates was bimodal, while in ethanol, it was unimodal. Moreover, in ethanol, an increase in the poly(methyl methacrylate) content caused a decrease in the hydrodynamic radius of aggregates. A significant difference in the nature of the blocks included in the brushes determines the selectivity of the used solvents, since their thermodynamic quality with respect to the blocks is different. The macromolecules of the studied graft copolymers tend to self-organization in selective solvents with formation of a core–shell structure with an insoluble solvophobic core surrounded by the solvophilic shell of side chains.

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