Mechanical properties of films and nanofibers made of biocompatible polymer nanocomposites with embedded molybdenum trioxide nanowires.

Abstract

Iskanje novih materialov z zanimivimi in uporabnimi lastnostmi je vedno v prid človeštvu. V zadnjih nekaj desetletjih so v središču raziskav tako nanodelci sami kot polimerni nanokompoziti z vgrajenimi nanodelci. V tem delu sem izdelal in okarakteriziral nanokompozit, sestavljen iz polimerov PVP in PVDF-HFP ter nanožic iz MoO$_3$. Za izdelavo nanožic MoO3 sem najprej s kemijsko transportno reakcijo sintetiziral nanožice Mo$_6$S$_2$I$_8$, nato pa te oksidiral. Polimera PVDF-HFP in PVP sta bila kupljena. Za izdelavo nanokompozita sem nato polimera PVDF-HFP in PVP posebej raztapljal v DMF-ju, raztopini PVP-ja sem nato dodal še nanožice MoO$_3$, nato pa obe raztopini zmešal skupaj. Iz te raztopine sem nato pripravil tanke filme s pomočjo vlivanja in nanovlakna s pomočjo elektropredenja. Za karakterizacijo sem uporabil SEM, s katerim sem videl, da nastajajo v filmih in vlaknih skupki, sestavljeni iz MoO$_3$ in PVP, ter da so nanovlakna debela okoli 150 nm, kar pa sem potrdil še z AFM-jem. Z AFM-jem sem opazil še, da so skupki na filmih visoki približno 60 nm. Z ramansko spektroskopijo je bila pri filmih ugotovljena nova vez pri 959 cm$^{-1}$, ki predstavlja novo vez O=Mo=O, ki pa je pri nanovlaknih nisem opazil. Posledica tega je, da MoO$_3$ ni dobro vezan na polimera, kar pa je privedlo do tega, da je bilo elektropredenje tega nanokompozita težavno. Za meritev mehanskih lastnosti sem uporabil DMA, kjer sem opazil, da ima film Youngov modul za red velikosti višji kot vlakna, saj so ta veliko bolj porozna, vendar pa kvantitativno nisem dobil dobrih podatkov, saj je bilo elektropredenje v velikih količinah težavno. Na koncu pa sem z meritvijo pH vrednosti videl, da se nanovlakna raztapljajo približno dvakrat hitreje kot filmi.The search for new materials with interesting and useful properties is always in the interest of mankind. In the last few decades, both nanoparticles themselves and polymer nanocomposites with embedded nanoparticles have been the focus of research. In this work, I produced and characterized a nanocomposite consisting of PVP and PVDF-HFP polymers and MoO$_3$ nanowires. To make MoO$_3$ nanowires, I first synthesized Mo$_6$S$_2$I$_8$ nanowires via a chemical transport reaction and then oxidized them, while PVDF-HFP and PVP polymers were purchased. To make the nanocomposite, I separately dissolved the PVDF-HFP and PVP polymers in DMF, then added MoO$_3$ nanowires to the PVP solution and the two solutions together. I then prepared thin films from this solution using casting and nanofibers using electrospinning. For characterization, I used SEM, with which I saw that aggregates consisting of MoO$_3$ and PVP are formed in the films and fibers, and that the nanofibers are about 150 nm thick, which I also confirmed with AFM. With the use of AFM I also noticed that the aggregates on the films are about 60 nm high. With Raman spectroscopy, a new bond at 959 cm$^{-1}$ was found in the films, which represents a new O=Mo=O bond, which I did not notice in the nanofibers. As a result, MoO$_3$ is not well bonded to the polymer, which led to difficulties of creating nanofibers via electrospinning. To measure the mechanical properties, I used DMA, where I noticed that the film has a Young\u27s modulus an order of magnitude higher than the fibers, since they are much more porous, but I did not get good quantitative data, since electrospinning in large quantities was difficult. In the end, by measuring the pH value, I saw that the nanofibers dissolve about twice as fast as the films