An octa-functional acrylate of C-tetramethyl calix[4]resorcinarene(CMC-4-RA) was facilely synthesized and characterized with 1H NMR, 13C NMR and FTIR spectroscopy. The CMC-4-RA was added to a thiol-acrylate system with different mass ratios, and exposed to a middle pressure mercury lamp. The maximum photopolymerization rate and final vinyl group conversion in the cured film increased greatly along with CMC-4-RA addition that was monitored with Photo-DSC. The tensile strength and pendulum hardness were improved significantly after the addition of CMC-4-RA. With increasing the content of CMC-4-RA to 60%(mass fraction), the glass transition temperature increased from 34.2 °C to 84.1 °C; the cross-link density was calculated to be increased from 23.83 mmol/cm3 to 82.40 mmol/cm3 according to dynamic mechanical thermal analysis; the thermostability was greatly improved.
A Aeries of hydroxylic hyperbranched polymers were derived from 2,2-bis(methylol) propionic acid and tris(methylol) propane reacted with acrylic acid to various extents. The obtained acrylated hyperbranched polymers alone or with a monofunctional diluent, isobornylene acrylate(IBOA) were further cured by UV radiation. The cured films based on the modified polymers alone all demonstrated poor mechanical properties due to their high network densities and low moving ability of polymer chains. For the composite systems, the cured films demonstrated improved mechanical properties due to the low network densities and high chain moving ability. With more IBOA included in the systems, acrylate groups can react to a higher extent during the curing process.
This work deals with the dependence of the z-average mean-square radius of gyration ( z) on the degree of branching(DB) for highly branched copolymers made from the one-pot cocondensation of AB 2 and AB monomers. A new expression of the degree of branching has been derived. The DB monotonously increases with increasing A group conversion and the fraction of AB 2 monomers. The value of DB calculated in accordance with our formula is lower than that given by Frey and coworkers. Howerver, when the reaction approaches completion, our expression of the degree of branching degenerates into the equation reported by Frey. Furthermore, the z-average mean-square of gyration of the resulting copolymer in the Θ state has been derived on the basis of the classical work developed by Stockmayer, Gordon, Li and Ba. The relationship between DB and z is illustrated by numerical results. The z-average mean-square radius of gyration of the copolymer with a certain weight-average molecular weight monotonously decreases with increasing the degree of branching.
