What is the physical meaning of the glass transition temperature Tg of the emulsion? How to adjust?

Glass transition temperature T. (Also known as the second transition temperature) refers to the temperature at which a polymer changes from an elastic state to a glass state, and is an important performance index of a polymer. The polymer exhibits elasticity above this temperature, and the polymer exhibits brittleness below this temperature. Polymer emulsion is a kind of high polymer, and its glass transition temperature reflects the hardness of the polymer emulsion after forming a coating film. Emulsion polymers used in architectural coatings are generally thermoplastic and are in a rubbery state at a certain temperature. It will gradually show rigidity when it is cooled, but it still retains deformable viscoelastic properties until it reaches the glass transition temperature. Once cooled below the glass transition temperature, the polymer becomes a glassy brittle substance and cannot form a film. The glass transition temperature of the emulsion depends on the composition of the copolymer. The hard monomer that can form a rigid polymer and the soft monomer that can form a soft polymer can be used in combination as needed. The glass transition temperature of the emulsion can also be adjusted twice by adding a plasticizer. However, plasticizers have problems of migration and volatilization, so attention should be paid to their application.