This study explored Candida antarctica Lipase B (CALB)-catalyzed condensation reactions to prepare high-purity, metal-free, polycarbonate polyols. Terpolymerizations of diethyl carbonate (D) with 1,8-octanediol (0) and tris-(hydroxymethyl)ethane (T) were performed in bulk at relatively low temperature (80 degrees C) using a pressure-varied two-stage process to minimize evaporative loss of diethyl carbonate. NMR experiments of resulting polycarbonate polyols, including analysis of proton NMR resonances by COSY spectra and carbon-13 resonances by HSQC, HSQC-TOCSY, and HMBC spectra,;Mowed determination of copolymer composition as well as relative percentages of linear, terminal, and dendritic T-units. With D/O/T monomer feed ratio 3:0.9:0.1, the highest values of dendritic T-unit content (83%) and M-w (23 900) by SEC-MALLS were attained. By decreasing D content in the monomer feed, the mol % of dendritic T-units in chains decreased to as low as 0%. By keeping the D/(O + T) ratio constant at 2.0 while increasing the ratio of O-to-T units from 9:1 to 7:3, dendritic T-unit content decreased from 51 to 28 mol %. At short reaction times (e.g., 4 h), highly functional linear terpolymers were formed. Increase in reaction time from 4 to 8, 12, 24, and 30 h resulted in increased dendritic unit content (0-48%), M-w/M-n (1.5-5.6), and relative M-w (2100 to 39000). Thus, immobilized lipase-catalyzed synthesis of polyol polycarbonates successfully enabled control of critical polymer structural parameters without formation of a gel fraction or product discoloration.