TECHNICAL FIELD

The present invention relates to a composite and a production method thereof.

BACKGROUND ART

It has been common knowledge that sliding surfaces having a polymer brush layer have a low friction coefficient. For example, Patent Document 1 discloses a sliding structure comprising a block having a polymer brush coating on a DLC-Si coating and a ring having a similar polymer brush coating.

In Patent Document 2, a detailed examination of a mechanism of sliding between polymer brush surfaces is performed using an atomic force microscope, and the technique disclosed therein enables micron-scale sliding between such brushes which an atomic force microscope can measure.

RELATED ART DOCUMENTS

Patent Document

Patent Document 1: JP-A 2012-56165

Patent Document 2: JP-A 2006-316169

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

On the other hand, in terms of stable, long-term use of materials having a sliding surface with such a polymer brush layer, excellent load bearing properties and durability have been required in addition to low friction sliding properties.

The purpose of the present invention is to provide a material having low friction sliding properties and having excellent load bearing properties and durability.

Means for Solving Problems

As a result of intensive studies to achieve the above object, the present inventors found that the object can be achieved by a composite wherein block copolymer chains are dispersed in a base polymer, the block copolymer chains comprise a polymer block (A) and a polymer block (B) having lower affinity for the base polymer than that of the polymer block (A), each of the block copolymer chains has the polymer block (A) at two or more locations, and in at least some of the block copolymer chains, the polymer blocks (A) are located in the base polymer and the polymer blocks (B) are exposed from the base polymer. This finding has led to the completion of the present invention.

Specifically, the present invention provides a composite comprising a plurality of block copolymer chains dispersed in a base polymer, the block copolymer chains comprising a polymer block (A) and a polymer block (B) having lower affinity for the base polymer than that of the polymer block (A),

wherein each of the block copolymer chains has the polymer block (A) at two or more locations of the block copolymer chain, and

in at least some of the block copolymer chains, the polymer blocks (A) are at least partially located in the base polymer and the polymer blocks (B) are at least partially exposed from the base polymer.

The present invention further provides a method for producing the composite, the method comprising the step of mixing the base polymer and the block copolymer chains, so that in at least some of the block copolymer chains, the polymer blocks (A) are located in the base polymer and the polymer blocks (B) are exposed from the base polymer. In this method, the mixing can be performed by any of the following methods: heating; mixing in a solvent; and mixing by dispersion.

The present invention also provides a method for producing the composite, the method comprising the steps of:

mixing the base polymer and the block copolymer chains under heat to prepare a molten mixture; and

cooling the molten mixture to cause a phase separation, so that in at least some of the block copolymer chains, the polymer blocks (A) are located in the base polymer and the polymer blocks (B) are exposed from the base polymer.

Effects of Invention

The present invention can provide a composite having low friction sliding properties and having excellent load bearing properties and durability.

