Hetero-difunctional dimers as building blocks for the synthesis of poly(amidoamine)s with hetero-difunctional chain terminals and their derivatives

This article reports on a simple and straightforward preparation method of poly(amidoamine)s (PAAs) with hetero-difunctional chain ends as well as of several up to now hardly obtainable PAA derivatives of biotechnological interest, such as for instance PAAs of controlled molecular weight and narrow polydispersity mono-functionalized at one end with an acrylamide group, PAAs with star-like molecular architecture, graft-PAA-protein conjugates, "tadpole-like" PAA conjugates with hydrophobic moieties able to self assemble into nanoparticles in aqueous media. The key step was to design suitable building blocks consisting of hetero-difunctional dimers (HDDs). In particular, the HDDs considered were the mono-addition products of bis-sec-amines and bisacrylamides expected to give PAAs of proven biomedical potential and were obtained as hydrochlorides or trifluoroacetates. In this form, they could be indefinitely kept dormant at 0-5 \ub0C in the dry state, whereas at room temperature and in aqueous media, they polymerized at pH > 7.5. The preparation of the above-cited PAA derivatives did not necessarily involve the preliminary synthesis of hetero-difunctional PAAs but was directly achieved by one-pot polymerization of HDDs in the presence of the substrates of interest. \ua9 2012 Wiley Periodicals, Inc