|Abstract:||Porous polymers have been prepared by emulsion templating and by using styrene as the monomer and divinylbenzene as the crosslinker. The polymerisation has been initiated with a radical initiator or by foto initiator. The amount of the crosslinker has been varied and its influence on morphology and amount of the remaining double bonds in the polymer matrix has been studied.
Methacrylic acid has been introduced into the mentioned polymer system, therefore carboxylic group was successfully incorporated into the polymer chain. Appropriate stability of the emulsion was achieved by combining different surfactants. The highest share of methacrylic acid that could be intergrated was 20 molar percentages. Thermal initiation of the free radical polymerisation lead to partial transfer of methacrylic acid into the internal phase. Therefore photoinitiation was used because of the faster conversion from monomer to polymer and methacrylic acid remained in the organic phase. This yielded in porous poyHIPE material, containing acid groups in the polymer chain and with a typical polyHIPE structure. Carboxylic groups have been functionalised by thionyl chloride to obtain acid chloride moieties. The rate of conversion was 76 percentages. Bifunctional amines have been used in order to verify the products reactivity. The influence of amine concentration and the lenght of its carbon chain on the conversion rate and the structure of the product have been studied. The conversion rate was 10 percent higher when using 1,12-diaminododecane compared to the conversion rate when using 1,4-diaminobutane. The higher concentration of the diamine enlarged the conversion rate when using 1,12-diaminododecane, whereas by using 1,4-diaminobutane this effect was not noticed.
Further on, porous poy(styrene-co-divininylbenzene) poliHIPEs have been prepared by varying the amount of the crosslinker from 37 to 80 molar percentages. The influence of the crosslinker amount on the BET surface area has been verified. A trend of increasing surface area with increasing the amount of the crosslinker has been noticed. Fourier transform infrared spectroscopy spectra have enabled us to determine the amount of the remaining double bonds in the polymer matrix. In order to incorporate functionalities into the polymer, functionalisation with multifunctional thiols was used. Thiols containing two and four thiol groups have been used. Furthermore, a bifunctional alkene has been incorporated onto the grafted polymer. The polymerisation efficiency was higher when using a higher degree of the crosslinker, the highest conversion rate was at 44 percent, where higher conversion rates were achieved when using the bithiol reagent. Mesopore size distributions have been compared between the unfunctionalised and functionalised samples and the latter revelaed a decrease in mesopore size. In was concluded that the solvent used was accountable for that. Also, a one-step functionalisation was performed, where bithiol and multifunctional alkene were included at once in the reaction mixture. In this case, a substantial increase in BET surface area was noticed, whereas the conversion rate was quite low.
Hereinafter, a hypercrosslinking approach has been utilised in order to incorporate mesopores and micropores into the poly(styrene-co-divinylbenzene) matrix. A peroxy initiator, namely di-tert-butyl peroxide, that has a specific mechanism of initiation, has been used. The amount of divinylbenzene in the untreated samples varied from 52 to 80 molar percentages. We were interested in the influence of the process on the morphology of the samples. It has been shown that the hypercrosslinking reaction does not influence substantially on the morphology of the material, the greatest difference in the morphology was found in the least crosslinked sample. Three solvents have been used for the hypercrosslinking reaction: toluene, acetonitrile and dimethylformamide. In the case of using toluene, the increase in the BET surface area was significant, the highest enlargment factor amounted to 7,2 folds.|