t-Butyl-Oxycarbonylated Diamines as Building Blocks for Isocyanate-Free Polyurethane/Urea Dispersions and Coatings.

t-Butyl-oxycarbonylated diamines ("di-Boc-carbamates") are investigated as dicarbamate monomers for diamine/dicarbamate polymerizations. Polyureas (PUs) and polyurethanes (PURs) with high molecular weights are prepared from stoichiometric polymerizations of diamines or diols with N-N'-di-t-butyl-oxycarbonyl isophorone diamine (DiBoc-IPDC) using KOt-Bu as a catalyst, while gelation is observed when an excess of DiBoc-IPDC is used with respect to the diamines or diols. Stable dispersions are obtained from PUs and PURs with 3,3'-diamino-N-methyldipropylamine (DMDPA) as internal dispersing agent. The corresponding PU-based coatings exhibit superior mechanical properties and solvent resistances compared to the polyurethane urea coatings synthesized from diols, DiBoc-IPDC, and DMDPA.

Chemoselective Alternating Copolymerization of Limonene Dioxide and Carbon Dioxide: A New Highly Functional Aliphatic Epoxy Polycarbonate.

The alternating copolymerization of biorenewable limonene dioxide with carbon dioxide (CO2 ) catalyzed by a zinc ß-diiminate complex is reported. The chemoselective reaction results in linear amorphous polycarbonates that carry pendent methyloxiranes and exhibit glass transition temperatures (Tg ) up to 135 °C. These polycarbonates can be efficiently modified by thiols or carboxylic acids in combination with lithium hydroxide or tetrabutylphosphonium bromide as catalysts, respectively, without destruction of the main chain. Moreover, polycarbonates bearing pendent cyclic carbonates can be quantitatively prepared by CO2 insertion catalyzed by lithium bromide.

Isocyanate-Free Approach to Water-Borne Polyurea Dispersions and Coatings.

Here, an isocyanate-free approach to produce polyureas from diamines and dicarbamates as monomers is reported. A side reaction limiting the molecular weight during the diamine/ dicarbamate polymerization, that is, N-alkylation of amine end groups, is investigated. Mitigation of the N-alkylation, either by enhancing the carbamate aminolysis rate or by substitution of dimethylcarbamates with more sterically hindered diethylcarbamates, affords polyureas with sufficiently high molecular weights to assure satisfactory mechanical properties. Stable polyurea dispersions with polyamines as internal dispersing agents are prepared, and the properties of the corresponding coatings are evaluated.

Unique Base-Initiated Depolymerization of Limonene-Derived Polycarbonates.

The depolymerization of poly(limonene carbonate) (PLC) initiated by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) was investigated. The strong organic base TBD was capable of deprotonating the OH-terminated PLC, leading to fast degradation via backbiting reactions at high temperature. An interesting feature of the base-initiated breakdown of PLC lies in the quantitative depolymerization into the corresponding initial limonene oxide monomer. This result implies the complete back-to-monomer recyclability of the fully biobased PLC, which accordingly can be considered as a really sustainable material. Additionally, the stability of PLC when exposed to TBD was enhanced by an end-capping reaction, which further supported the proposed degradation pathway.