Polyamines, such as PEI (poly ethylene imine), are cationic polymers with a vast variety of applications.  PEI and derivatives thereof are used in e.g. pulp and paper production to overcome manufacturing problems caused by resins and mechanical pulp extractives (Mönch D, Stange A, Linhart F, Advanced Product Concepts for Concomitant Elimination and Increased Efficiency of Paper Manufacture, Wochenblatt für Papierfabrikation 1996, 124:889-892, 894-895).  The charged nature of the polymer also makes it useful for immobilization of e.g. enzymes (Grunwald P, Freder R, Gunsser W, Application of polyethylene imine as carrier material for enzyme immobilization Naturwissenschaften 1981, 68:525-526); (de Lathouder K M, van Benthem D T J, Wallin S A, Mateo C., Fernandez Lafuente R, Guisan J M, Kapteijn F, Moulijn J A, Polyethyleneimine (PEI) functionalized ceramic monoliths as enzyme carriers: Preparation and performance Journal of Molecular Catalysis B: Enzymatic 2008, 50:20-27). 
Recently advances have been made in gene delivery where PEI, sometimes in combination with PEG, has shown to increase the cell penetration of DNA/RNA (Lung-witz U, Breunig M, Blunk T, Göpferich A, Polyethylenimine-based non-viral gene delivery systems European Journal of Pharmaceutics and Biopharmaceutics 2005, 60:247-266); (Belenkov A I, Alakhov V Y, Kabanov A V, Vinogradov S V, Panasci L C, Monia B P, Chow T Y. Polyethyleneimine grafted with pluronic P85 enhances Ku86 antisense delivery and the ionizing radiation treatment efficacy in vivo.  Gene Therapy 2004, 11:1665-1672.); ( Jeong J H, Kim S W, Park T G. A new antisense oligonucleotide delivery system based on self-assembled ODN-PEG hybrid conjugate micelles.  Journal of Controled Release.  2003, 93:183-191.)  This is a very promising application since the concept of ADN (antisense oligonucleotides) was introduced, and received the Noble prize in the Year 2006.  Successful delivery of an anticoding gene would cure a plethora of diseases such as HIV, cancer, autoimmune responses etc.  Further therapeutic applications of polyamines include relief of symptoms related to skin diseases and chemotherapy. 
The currently available polyamines such as PEI and dendrimers are synthesized in organic solvent.  The conventional polymerization of ethylene imine is based on ring opening, thus limiting the length of the repetitive unit to two carbons between the nitrogen atoms. 
The problem to be solved by the present invention is, therefore, to provide a method of preparing polyamines which may be performed in aqueous environment, and which is not limited to C2-building blocks.