Abstract
Thermo- and pH-responsive poly(N-[3-(diethylamino)propyl]methacrylamide)s were synthesized by free radical polymerization and RAFT polymerization. The molar masses of the samples were 33,000–35,000 g∙mol−1. Investigations of the dilute solutions showed that the prepared samples were flexible chain polymers. The behavior of the synthesized polymers in the buffer solutions was analyzed by turbidity and light scattering at a pH range of 7–13 and a concentration range of 0.0002–0.008 g·cm−3. When the concentrated solutions were at a low temperature, there were macromolecules and aggregates, which were formed due to the interaction of hydrophobic units. For the investigated samples, the lower critical solution temperatures were equal. The phase separation temperatures decreased as pH increased. The influence of polydispersity index on the characteristics of the samples in the solutions was analyzed. The radii of molecules of poly(N-[3-(diethylamino)propyl]methacrylamide) obtained by RAFT polymerization at this temperature at the onset and end of the phase separation interval were lower than ones for samples synthesized by conventional free radical polymerization.
Highlights
In recent decades, special attention has been given to polymers manifesting thermoand pH-responsive properties, the combination of which enables new possibilities for the use of polymers, especially in the field of drug delivery [1,2]
It is known that an increase in the hydrophobicity of the initial amine-containing acrylamide results in a thermoand pH-responsive polymer [11,12,13]
It is clearly shown that Mw of PDEAPMA-C and PDEAPMA-R coincide in the range of experimental error
Summary
Special attention has been given to polymers manifesting thermoand pH-responsive properties, the combination of which enables new possibilities for the use of polymers, especially in the field of drug delivery [1,2]. Polymers based on N-alkyl acrylamides are one of the most studied and used classes of thermoresponsive polymers, while amino-containing derivatives of poly(methacrylamide)s remain insufficiently studied. In the field of stimuli-responsive materials, DMAPMA is primarily used as a comonomer to impart pH-sensitivity to hydrogels based on acrylic monomers [3,4,5,6,7,8]. It is known that an increase in the hydrophobicity of the initial amine-containing acrylamide (e.g., through the introduction of the second alkyl substituent in the amide group or the replacement of methyl substituents by ethyl ones in the amino group) results in a thermoand pH-responsive polymer [11,12,13]. Approaches are being developed to obtain homopolymers of dialkylaminoalkyl(meth)acrylamides [11,12,14] and their stimuli-sensitive copolymers [12,13]
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