Method for producing polymer nanocomposite, and flame-retardant polymer nanocomposite formed by the production method

A method for producing a polymer nanocomposite, comprising:

• after expanding an interlayer space of a layered inorganic compound using an organic onium salt, immobilizing a radical polymerization initiator having a group represented by general formula (1) shown below on an interlayer surface of the layered inorganic compound via a covalent bond;
• and
• carrying out surface-initiated radical polymerization in a monomer from the immobilized radical polymerization initiator:
• wherein, R1 represents a C1-25 alkylene group, a C2-25 alkenylene group, a C5-8 cycloalkylene group, or a C6-12 arylene group, each of which being optionally substituted by a C1-18 alkyl group, a phenyl group, or a cyano group and being optionally interrupted by an oxygen atom, a carbonyl group, an ester group, a phenylene group, an amide group, or an imino group, the substitution and the interruption being optionally combined with each other;
• and X1 to X3 each independently represent a halogen atom, a hydroxy group, a methyl group, an ethyl group, a methyloxy group, or an ethyloxy group.