Fully-​biobased poly(limonene carbonate)​s as novel coating resins

Hydroxy-​ended poly(limonene carbonate)​s (PLCs) have been prepd. by copolymn. of limonene oxide with CO2, using a β-​diiminate zinc-​bis(trimethylsilyl)​amido complex as the catalyst, and subsequent transcarbonation reactions using various (metallo)​org. catalysts​/polyol systems, viz.stannous octoate, (salen)​AlEt (salen=2,​2'-​ethylenebis(nitrilomethylidene)​diphenol) and 1,​5,​7-​triazabicyclo-​[4.4.0]​dec-​5-​ene as the transcarbonation catalysts, combined with 1,​10-​decanediol, 2-​(hydroxymethyl)​-​2-​ethylpropane-​1,​3-​diol and pentaerythritol as the transcarbonation agents. The structure and end groups of the polymeric species in the PLCs were identified by MALDI-​ToF-​MS. For the first time, the α,​ω-​dihydroxyl PLCs were used in solvent casting and curing. Although only moderate properties were achieved so far due to incomplete curing, the fully bio-​based PLCs with adequate mol. wts. and glass transition temps. are considered as promising resins for coating applications. Preliminary expts. on the modification of the pendant isopropenyl groups of PLC by thiol-​ene reaction with mercapto alcs. carrying primary OH functionalities showed promising properties like acetone resistance, reverse toughness after curing with a polyisocyanate. Direct curing of PLCs using polyfunctional thiols also gave the coatings with good properties.