Abstract: Crosslinked polycondensation products of: (a) polyols selected from the group consisting of: (1) polyols with three or more hydroxyl groups, (2) acetal forms of (1), and (3) mixtures thereof, and (b) polyacids selected from the group consisting of: (1) polyacids with two or more carboxylic groups, (2) anhydrides of (1), (3) esters of (1), and (4) mixtures thereof are disclosed. The resulting polyesters have a molar ratio of polyol to polyacid from about 1:3 to about 3:1 and are highly-crosslinked. Preferred monomers are sustainable monomers such as glycerol, citric acid, fumaric acid, and sebacic acid. Two-step heating processes for preparing the high molecular weight polyesters are also provided.