| Abstract
| - Tensile properties and morphology of tetrafunctional multigraft copolymers are investigateddependent on PS volume fraction and number of branch points. It is found that tetrafunctional multigraftcopolymers with 22 vol % PS and seven branch points show a surprising high strain at break of about2100%, about double that of commercial thermoplastic elastomers (TPE's) such as Kraton. With increasingnumber of branch points, strain at break and tensile strength increases, and strain at break is about2300% for a sample with 10 branch points. Investigation of morphology using transmission electronmicroscopy indicates that a sample with 22 vol % PS has a wormlike microphase-separated structurewith much lower long range order than other TPE's s such as Kraton. The multigraft copolymers of thisstudy have two PS arms at each branch point. This, together with a large number of branch points permolecule, allows the elastic PI backbone to couple into a large number of reinforcing PS domains, resultingin huge elasticity, combined with a high tensile strength. Two parameters for adjusting mechanicalproperties of multigraft copolymers are found in our investigations: (1) functionality of the graft copolymer,tri- or tetrafunctional, and (2) number of branch points per molecule.
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