IR spectral studies were performed for poly(1H,1H-fluoroalkyl alpha-fluoroacrylate)s [-{CH2CFC(O)OCH2(CF2)(n)Y}(p)-, Y = H or F, n = 1-11] in a wide temperature range. The carbonyl absorptions [nu(C=O)] split into two peaks near 1770 +/- 4 (nu(1)) and 1795 +/- 4 (nu(2)) cm. The ratio in absorbances of nu(2) to nu(1) increased with increasing crystalline region formed by the main chains but was independent of that formed by the fluoroalkyl side chains. The present IR results revealed that both the main and fluoroalkyl side chains participate in the formation of crystallites, but in the shorter fluoroalkyl homologoues with n < 7, the main chains including C=O groups in the esters mainly form the crystallites, while in the longer fluoroalkyl homologues the side chains predominate over the main chains to form the crystallites, although an ordering of main chains still exists. Moreover, the C=O bonds were considered to be in cis conformation to alpha C-F bonds in the main chain crystallites and almost in a perpendicular direction to the main chains.