Thermal Characterization of Crosslinked Polymeric Microspheres Bearing Thiol Groups Studied by TG/FTIR/DSC under Non-Oxidative Conditions  
[PERSON]  
1 Department of Polymer Chemistry, Institute of Chemical Sciences, Faculty of Chemistry, Maria Curie-Sklodowska University, 20-614 Lublin, Poland; [EMAIL_ADDRESS]  
[PERSON]  
2 Department of Organic Chemistry and Crystal Chemistry, Institute of Chemical Sciences, Faculty of Chemistry, Maria Curie-Sklodowska University, 20-614 Lublin, Poland; [EMAIL_ADDRESS]  
[PERSON]  
1 Department of Polymer Chemistry, Institute of Chemical Sciences, Faculty of Chemistry, Maria Curie-Sklodowska University, 20-614 Lublin, Poland; [EMAIL_ADDRESS]  
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packings for chromatography and solid phase extraction [23; 24; 25; 26], supports for solid-phase organic synthesis in the preparation of oligopeptides or various monosaccharide derivatives, substrates for the heterogenous catalysts used in organic chemistry [27] and matrices for nanocomposite synthesis with metals like silver, gold or quantum dots [28; 29; 30].  
The incorporation of thiol groups into the structure of polymer microspheres has been reported in the literature most often as a multi-stage process. Since it involves the presence of a halomethyl group, polymer networks containing aromatic rings susceptible to electrophilic aromatic substitution are usually preferable. The halomethyl groups undergo the reaction with a suitable sulfur compound giving an intermediate product that must be hydrolyzed in a subsequent step to obtain the thiol group [21; 22; 31; 32; 33]. The described methods are time-consuming, the reactions involved must be carried out with catalysts and in organic solvents, and often involve harsh conditions for porous microspheres, which can destroy their porous structure or even the entire microsphere. In our previous paper [34], a new method for the modification of polymer microspheres with thiol groups was presented. Crosslinked, porous GMA-based copolymer microspheres possessing thiol groups in their chemical structure were obtained in the reaction with thiocarboxylic acids in a one-step process in a short time and in a catalyst- and solvent-free environment. These reaction conditions preserve the permanent internal porosity and the spherical structure of the polymer particles.  
We also reported [34] the thermal properties of these new copolymers studied in an oxidative atmosphere. The purpose of the present investigation was to characterize the thermal behavior of porous copolymer microspheres of GMA crosslinked with benzene-1,4-diylbis(2-methylprop-2-enoate) (1,4 DMB), (poly(GMA-\(\infty\)-1,4 DMB)) and GMA crosslinked with TRIM (poly(GMA-\(\infty\)-TRIM)) and their derivatives bearing thiol groups in non-oxidative conditions. To our knowledge, the results of the behavior of these copolymers during pyrolysis have not been reported in the literature. However, it is an important issue, especially in terms of copolymer recycling and possible reuse of polymeric sorbents. In this study, an analysis was conducted before and after the modification of microspheres with thioglycolic acid using thermogravimetric analysis (TG) coupled with FTIR spectroscopy, differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR). The use of NMR as a tool for the detection of volatiles is a novel approach enabling more complete identification of polymer degradation products. Additionally, the thermal degradation pathways of the starting and thiol-functionalized microspheres are presented based on their degradation products.