SOURCE:

Faculty: Physical Sciences
Department: Pure And Industrial Chemistry

CONTRIBUTORS:

Ofoegbu,O.
Eboatu, A. N.
Okoye, P. A. C.

ABSTRACT:

Degraded products from tobacco smoking have been causing lots of health challenges to both smokers and non-smokers with increasing health and economic burden to the society. Efforts by various governments to create smoke free environments by way of imposing restrictions and taxes to curb the associated challenges, has been unsuccessful. Cigarette manufacturers introduced filter materials with supposed prevention of the ingestion of the dangerous components of the smoked tobacco products. The butt filters have challenges of performance efficiency, non-degradability and environmental pollution; hence this research is aimed at finding a better alternative filter materials. This study presents the syntheses of molecularly imprinted polymer (MIP) filter materials for sequestration of the toxicants from degraded tobacco products. Proton NMR (1H NMR) titration was first carried out to select the suitable monomer-template reacting ratio for the syntheses using chitosan (CS) as recognition matrix. A proof-of-concept experiment was carried out by using the best result from the (1H NMR) titration to produce CS-based thin film materials selective for nicotine and 3-phenylpyridine (tobacco specific nitrosamine analogues). These were deposited on quartz crystal resonators of a. Quartz Crystal Microbalance (QCM). The results from the QCM guided the bulk polymerization experiments which were carried out via non-covalent polymerization method. CS served as the natural functional monomer, Methacrylic acid (MAA) as graft-monomer, 1,4 Bis (acryloyl) piperazine (BAP) and geranic acid (GA) as synthetic and natural cross linkers respectively. Nicotine, Phenylalanine amide (tobacco specific nitrosamine analogue) and a 50:50 blend of the individual materials were employed as templates and phosphate buffer saline solution (pH 7.4) as porogen. Reaction temperatures of 70oC and reaction time of 12 h (water bath heating), 4 mins for (microwave heating) were applied. The functional groups were identified and polymerization confirmed using Fourier Transformed Infra-red Spectroscopy (FTIR). Particle and pore sizes, surface area and pore volume were determined using the Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods. The thermal, surface morphology and cavity integrity were also ascertained using Simultaneous Thermal Analyzer (STA), Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) respectively. Rebinding studies was done using high performance liquid chromatography (HPLC) technique and UV-VIS spectroscopy. The results from 1H NMR titration showed proton chemical shifts on the phenyl ring at between 6.5 to 7.5 ppm as a downfield shift when the monomer: template ratio was adjusted from 1:1 to 4:1 and temperature increased from 30oC to 40oC to 60oC. The SEM confirmed the morphologies to be spherical intercalate. TEM showed samples with heterogeneous nanocavities within the size range of 214 nm and 22 nm. The FTIR result showed CS, MAA and BAP characteristic assignments. Overlap in transmittances occurred at wavenumbers, 954.19, 1695.94, 1293.39, 1435.03, 2174.9 and 3073.13 cm.-1 CS and MAA on cross-linking with BAP, gave a matrix with distinct peaks at 1110.75 (secondary alcohol C-O stretch), 1470.43 (carboxylic acid of MAA after cross-linking with CS), 1649.35 (primary amine N-H bend), 2126.45 and 3324.79 cm-1 (OH stretch and N-H stretch of primary amine). BET isotherm showed the samples to be of reversible type IVa hysteresis with H3 loop type of non-rigid aggregates. STA results gave samples’ decomposition temperatures to be above 250OC and a relative loss in mass of less than19% over a period within 50 mins of heating. A molecularly dual-templated filter material that shows superior potentials than the conventional cellulose acetate filter has been successfully prepared. The good result obtained from the proof-of-concept experiment supports the use of CS as matrix in thin film biosensing activities without the inherent swelability of CS in fluids within protic environments.