# Synthesis and Selected Properties of Ester Elastomer Containing Sorbitol
## 1 Introduction  
Due to environmental concerns, obtaining biodegradable polymers synthesized by utilizing monomers possible to acquire from renewable sources became a topic of interest among various researchers. One such group of materials is sugar alcohol-based polymers. The most researched materials of this type are glycerol-based. They have been proven to have many possible biomedical applications [1; 2; 3; 4; 5; 6; 7; 8; 9; 10]. Various polymers obtained using sorbitol as monomers include sorbitol-based terpolyesters [11] and biocompatible polymers based on sebaic acid and different sugar alcohols, including sorbitol [12]. A biocompatible polymer based on sorbitol and sebaic acid was also obtained [13]. Copolymers with succinic acid, sorbitol and different diols were also obtained and tested [14]. A sorbitol-based polymer with citric and sebaic acid as monomers and its biodegradability was also described in earlier work [15]. Sorbitol can also be used as a chain extender in self-healing polyurethane [16]. Biodegradable composites with hydroxyapatite in a poly(sorbitol sebaacate malate) matrix can also be obtained [17].  
Various examples of sugar alcohol-based polymers have been described in the literature. Polyesters were obtained using different xylitol-sebaic acid ratios. Their properties were tested, and the elastomers have been proven to be biocompatible in vitro [18]. Xylitol-based polymers synthesized using citric and sebaic acid were obtained. Poly(xylitol-co-citrate) was then copolymerized with methacrylic anhydride. The materials have been proven to be biocompatible in vivo [19]. Copolymers with two dicarboxylic acid segments were also synthesized and tested [20]. Sugar alcohol-based polymers have also been proven to be possible to synthesize using lipase as a catalyst [21]. Exact structure of non-cross-linked poly(xylitol sebaacate) has also beendetermined and proven to be a linear chain. The polymer contains mostly 1,5-diacyl and 1-acyl substitutions [22]. Other interesting materials obtained using sugar alcohols include: nanocomposites of poly(mannitol sebacate) with cellulose nanocrystals which display shape-memory properties [23], poly(xylitol-co-maleate-co-PEG) hydrogel, which can be used in order to encapsulate and inject cells [24], poly(xylitol sebacate), which can be electrospun by a core-shell method in order to obtain tissue-like material [25; 26], biodegradable poly(xylitol-dodecenoic acid) with possible future tissue-engineering applications [27], polymers able to reversibly solidify and liquefy, synthesized utilizing sugar alcohol and azo compounds [28], and conetworks based on poly(lactide) and sugar alcohols as core molecules [29].  
In this work we focus on obtaining three-monomer-based copolyesters and analyze how changing the polycondensation time affects the mechanical and thermal properties of resulting material. The novelty in this work is that, to the best of our knowledge, material obtained using exactly those monomers has not yet been synthesized. It is also of importance that one of the monomers used--sorbitol--can be obtained from renewable sources.