Elastic deformations of uniformly orientated layers of thermotropic polymeric comblike nematic in magnetic field were studied using the method of Freedericksz transitions. The temperature dependences of splay K-1 and bend K-3 elastic constants and optical anisotropy were determined. On clanging of the relative temperature Delta T = T - T-o from -0.5 to -60 degrees C, the optical anisotropy increases from 0.05 to 0.1. This experimental fact shows double increase of order parameter. It was found that in investigated temperature range the splay constant values are slightly more then the bend constant values (K-1/K-3 similar to 0.8).