The influence of photopolymerization reaction kinetics on diffraction efficiency has been investigated on the mixtures of photocurable acrylic monomer/nematic liquid crystals subjected to photopatterning. Photodifferential scanning calorimetry and real-time Fourier transform infrared spectroscopy experiments were conducted as a function of concentration in order to determine the reaction kinetics of acrylic monomer/liquid crystal mixtures. The lumped reaction rate constants for each concentration exhibited a nonlinear variation of the reaction rate constant with conversion and concentration. To gain fundamental insight, theoretical modeling and numerical simulation have been carried out by combining Flory-Huggins free energy of isotropic mixing and Maier-Saupe free energy of nematic ordering in conjunction with the experimentally determined reaction rate constants. The evolution of diffraction efficiency is discussed in terms of photopolymerization rates, monomer concentrations, and also the type of diffusion such as Fick diffusion occurring in a single phase or mutual diffusion in phase separating systems.