The influence of temperature and reactor size on photopolymerization kinetics of n-butyl acrylate (n-BA) using narrow channel reactors has been investigated. Experimental results have shown that increase in temperature and decrease in size of the reactor increases the monomer conversion. The effect of temperature was studied by immersing the reactor in a water bath maintained at different temperatures. A narrow channel glass reactor, 900 mm long, with diameters 1.5 mm, 1.0 mm, and 0.5 mm respectively were used to study the effect of light penetration depth on the rate of polymerization and molecular weights of the polymer produced. The degree of branching in the polymer produced was also estimated and compared with published data. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 1940-1947, 2010