Communication Macromolecular Rapid Communications 1846 Macromol. Rapid Commun. 2011, 32, 1846−1851 © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/marc.201100532 wileyonlinelibrary.com 1. Introduction During the last years, polymer chemistry and material sci- ence have seen significant advance in the use of renew- able resources in a variety of applications. In the area of polymer science, a broad pool of renewable compounds is discussed, [1] including mainly plant oils, [2] glycolides (e.g., lactic acid), [3] and furfural compounds. [1,4] Compared to those approaches a rather small amount of work was dedi- cated to the use of terpenes, although they found use as monomers too. [5] Betulin (lup-20(29)-ene-3 β,28-diol, Figure 1) is a nat- urally occurring triterpene containing two hydroxyl groups and one isobutylene unit. Its content in the birch bark can be as high as ≈30%, depending on the birch spe- cies, and it can be easily extracted from birch bark with the help of common organic solvents. There are many therapeutic formulations and also cosmetics based on betulin. The rising interest toward betulin and its deriv- atives in medicine is provoked by its biological activity. It has been shown that betulin derivatives exhibit anti- septic, anti-inflammatory, anticarcinogenic, and anti- oxidant activities. [6,7] Apart from pharmaceutical uses of birch bark extract, there have been few attempts to synthesize polyesters and polyurethanes based on bet- ulin back in the 1980s. [8–10] Due to the fact that birch bark is a large-scale waste product of the wood industry, the enormous potential of betulin-based chemicals is evident. Herein we report the use of betulin for the syn- thesis of highly porous polyester networks with high surface areas from betulin. Furthermore, we will discuss the synthesis of hyperbranched polyesters and linear polyesters, which show potential as gas separation membranes. Microporous polymers, i.e., polymers possessing per- manent pores smaller than 2 nm, are currently inves- tigated in great deal as they have high potential in a variety of applications, including gas separation/storage, Betulin, an abundant triterpene, can be extracted from birch bark and can be used as a renew- able monomer in the synthesis of microporous polyesters. Cross-linked networks and hyper- branched polymers are accessible by an A 2 + B 3 reaction, with betulin being the A 2 monomer and B 3 being a trifunctional acid chloride. Reaction of betulin with a diacid dichloride results in linear, soluble polyesters. The present communica- tion proves that the polyreaction follows the classic schemes of polycondensation reactions. The resulting polymers are analyzed with regard to their micro-porosity by gas sorption, NMR spectroscopy, and X-ray scattering methods. The poly- mers feature intrinsic microporosity, having ultrasmall pores, which makes them candidates for gas separation membranes, e.g., for the separation of CO 2 from N 2 . Intrinsically Microporous Polyesters From Betulin – Toward Renewable Materials for Gas Separation Made From Birch Bark Jekaterina Jeromenok, Winfried Böhlmann, Markus Antonietti, Jens Weber* J. Jeromenok, Prof. M. Antonietti, Dr. J. Weber Department of Colloid Chemistry, Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany E-mail: jens.weber@mpikg.mpg.de Dr. W. Böhlmann University of Leipzig, Faculty of Physics and Geosciences, Linnéstr. 5, 04103 Leipzig, Germany