A mean-field model of acentric order of dipolar chromophores in polymeric electro-optic materials is developed by extension of our earlier results [Y.V. Pereverzev, O.V. Prezhdo, Phys. Rev. E 62 (2000) 8324] to allow for position and orientation flexibility of chromophore dipoles with respect of the molecular frame. The extended model quantitatively reproduces the experimental data for two sample chromophore systems. The model indicates that the disappearance of the acentric order and the related turnover and decay of the electro-optic coefficient are associated with a second-order phase transition in the dipolar system from para- to antiferroelectric state.