Five crystalline phases have been characterized in the perovskite layer compound (C10H21NH3)2CuCl4, using differential scanning calorimetry, X-ray diffraction and infrared spectroscopy. The ordered phase V contains three types of hydrocarbon chains; two of them have an almost extended configuration with a gauche bond in the proximity of the NH3 group, the other one is the planar all-trans form. The proportion of the different forms varies as a function of temperature from 100 K to 306 K within phase V. The crystallographic symmetry of phases V and IV is triclinic while phases II and I belong to the monoclinic and orthorhombic systems respectively. When raising temperature, two discontinuous transitions, V-III and III-II, affect the interlayer distances and are related to the presence of conformational defects of the type gt3g- and gtg-, respectively, as well as to a relative disorder in the chain orientations. When decoupling the III-V transition by cooling, the abrupt change in the lattice parameters occurs between phases III and IV. The high temperature II-I transition is athermic and implies only a continuous structural modification from the monoclinic to the orthorhombic symmetry.