If you imply links between the molecules of polymers, but not component parts of these molecules, forces of bonds between them are Van-der-Vaal's forces( without the transmission of electrons from atoms ), i.e. intermolecular. Polymerization of molecules looks, as growth of loops on the surface layer of catalyst- one molecule grows from an active center, and then a free end is adsorbed by the surface of catalyst and fastened ( it looks as knitting of lace)) On other end of molecule a monomer initiate the growth of loop.By formation of row of such loops a primary lamel is formed,the separate loops of which are connected by intermolecular forces .A primary lamel is a basis for crystallization of new areas of growing chain. This chart works at the design of fibrils or other anisometric matters too. The weakness of these connections is deceitful, because at sufficient length of filaments sum of energies of these links is more than sum of energies of links which filaments are built from . Therefore even such loosely-coupled links are rarely broken by the fluctuations of thermal energy.