Characterization of monomer sequence structure distribution of poly(1-butene)/poly(propylene-co-butene) in-reactor alloys through 13C-NMR

In situ FTIR testing demonstrated that crystallization of novel poly(1-butene)/poly(propylene-co-butene) in-reactor alloys from melt shows thermodynamic stable Form I directly rather than general reported unstable crystal Form II. In order to make clear this phenomenon, the microstructure and monomer sequence distribution of the as-obtained poly(1-butene)/poly(propylene-co-butene) in-reactor alloys was determined by ¹³C-NMR. The raw alloy was separated by fractional dissolution to five grades. The characterization of raw alloys and different grades demonstrates that propylene monomer unit distributes in a form of isolated or segmented along poly(1-butene) molecular chains. The fractional dissolution of the selected alloy indicates that chain structure changes gradually with fractional solvent. The number average sequence length of propylene and 1-butene unit has been calculated. The number average sequence length and distribution could help us to study the crystallization and transformation clearly. From the results of in situ FTIR and NMR, the random distribution of the propylene unit with certain content in the as-obtained alloys play role to accelerate the crystallization transformation.