NOVELTY - Nanocomposite material (I) comprises rubber and a modified layered double hydroxide comprising: a charge-balancing organic ion having a first functional group and a second functional group, where part of the organic anions is chemically linked to the rubber through the second functional group; and/or a silane coupling agent having at least one alkoxysilane group and at least one reactive group, where the alkoxysilane group is chemically linked to the layered double hydroxide and the reactive group is chemically linked to the rubber.    USE - (I) is useful: in tyres, where the rubber is preferably a natural rubber or SBR; and in solar cell units, where the rubber is a silicone rubber (claimed). (I) is useful in e.g. green tyres, truck tyres, aircraft tyres; latex products e.g. gloves, condoms, balloons, catheters and foam; civil engineering products e.g. bridge bearings; non-tyre automotive applications e.g. engine mounts, rubber bearings and seals; milking inflations; and coating products e.g. pressure-sensitive adhesives and plastic hardcoats.    ADVANTAGE - (I) has improved heat stability, better dimensional stability, improved tear strength, improved scratch resistance, improved puncture resistance, increased flame resistance, increased adhesive power, and/or improved strength-to-weight ratios. (I) exhibits improved elongation and strength at break; better mechanical and dynamic properties; and improved viscoelastic properties. (I) has reduced permeability towards gases and/or liquids, such as nitrogen, carbon dioxide, oxygen, water vapor, and hydrocarbons. (I) reduces the processing time of the tyres, increases production rate of tyres and leads to improved process safety. (I) increases the lifetime of the solar cell unit and provides improved light yield and solar energy recovery.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a masterbatch comprising rubber (30-90 wt.%) or a rubber precursor and the modified layered double hydroxide (10-70 wt.%); and    (2) a preparation of the rubber precursor or (I), comprising: adding the modified layered double hydroxide, optionally mixed with a first solvent, to a rubber precursor comprising one or more polymers and optionally a second solvent; or adding the modified layered double hydroxide, optionally mixed with the first solvent, to a rubber composition comprising one or more monomers of the rubber precursor and optionally a second solvent, and polymerizing the monomers to form the rubber precursor; and optionally cross-linking the rubber precursor in the presence of a cross-linking agent to form the nanocomposite material; and optionally removing the first and/or second solvents during or after any one of the adding step or cross-linking step.