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Open AccessArticle

The Influence of Initiator Concentration on Selected Properties on Poly-N-Vinylcaprolactam Nanoparticles

Department of Physical Chemistry, Pharmaceutical Faculty, Wroclaw Medical University, Borowska 211, 50-556 Wroclaw, Poland
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Author to whom correspondence should be addressed.
Nanomaterials 2019, 9(11), 1577; https://doi.org/10.3390/nano9111577
Received: 30 September 2019 / Revised: 25 October 2019 / Accepted: 28 October 2019 / Published: 7 November 2019
The thermosensitive polymers of N-vinylcaprolactam P1, P2, P3, P4, and P5 were synthesized via the surfactant free precipitation polymerization (SFPP) at 70 °C in the presence of cationic initiator 2,2’-azobis[2-methylpropionamidine] dihydrochloride (AMPA). The influence of various concentrations of initiator AMPA on particle size, aggregation and lower critical temperature solution (LCST) was investigated by dynamic light scattering (DLS) measurement. The conductivity was measured in the course of the synthesis and during temperature decrease of the reaction mixtures. The polymers were characterized by Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR), 1H NMR, and thermogravimetric analysis. Thermal parameters of the degradations process were investigated using thermogravimetric analysis (TGA/DTA) under non-isothermal conditions in N2 atmosphere. The samples were characterized by powder X-ray diffraction analysis (PXRD).The hydrodynamic diameter (HD), polydispersity index (PDI) and zeta potential (ZP) were measured in aqueous dispersions of the synthesized polymers in temperature 18–45 °C. HD and PDI values at 18 °C were 137.23 ± 67.65 nm (PDI = 0.53 ± 0.18), 83.40 ± 74.46 nm (PDI = 0.35 ± 0.08), 22.11 ± 0.29 nm (PDI = 0.45 ± 0.05), 29.27 ± 0.50 nm (PDI = 0.41 ± 0.04), 39.18 ± 0.57 nm (PDI = 0.38 ± 0.01) for P1, P2, P3, P4, and P5, respectively. The aqueous solutions of the obtained polymers at 18–45 °C had a positive charge. ZP’s for P1, P2, P3, P4, and P5 polymers at 18 °C were 11.64 ± 4.27 mV, 12.71 ± 3.56 mV, 3.24 ± 0.10 mV, 0.77 ± 0.28 mV, 1.78 ± 0.56 mV respectively. The LCST range was between 32 and 38 °C. We conclude that the concentration of initiator affects the size of obtained polymeric spheres and theirs LCST. View Full-Text
Keywords: nanoparticles; N-vinylcaprolactam; 2-acrylamido-2-methyl-1-propanesulfonic acid; lower critical temperature solution; cationic initiator; conductivity nanoparticles; N-vinylcaprolactam; 2-acrylamido-2-methyl-1-propanesulfonic acid; lower critical temperature solution; cationic initiator; conductivity
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MDPI and ACS Style

Gola, A.; Niżniowska, A.; Musiał, W. The Influence of Initiator Concentration on Selected Properties on Poly-N-Vinylcaprolactam Nanoparticles. Nanomaterials 2019, 9, 1577.

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