The area of his work was soft matter physics, liquid crystals, electronics, molecular physics and condense matter physics.
He investigated properties of huge number of new matterials, effects and medium for electronics, optoelectronics and biological structures.
He developed new methods for modeling functions, molecular structure investigation and liquid crystal indicators.
Derjanski build Laboratory for Nuclear Magnetic Resonance in the Institute of Physics at the Bulgarian Academy of Sciences (1958).
He was founder of the Bulgarian liquid crystal scientific group and Laboratory of Liquid Crystal in the Institute of Solid State Physics (1968 – 1992).
He was head of the Laboratory of “Physical Chemistry of membrans” in the Central Laboratory of BAS (1982 – 1988).