Solvent-free fluidic materials possessing optoelectronic functions are expected to be major components in soft electronics applications. Conjugated polymers are promising targets for this purpose and their design approaches are classified into three types with respect to their structure: conjugation breaking (Type I), copolymerization with flexible polymers (Type II), and side chain engineering (Type III). In this short review, we highlight several early attempts to produce Type III conjugated polymers. We also present fully characterized Type III fluids recently developed by our group, with a brief summary of the structure–property relationship and fluidity-oriented functions.Introduction1 Polymer Design1.1 Fluidity of Polymeric Materials1.2 Type III CPs with T g < 25 °C1.3 Fluidification of Polyfluorenes1.4 Effect of Side Chain Length2 Fluidity-Oriented Functions2.1 Mechanofluorochromism2.2 Consistent Luminescence in Wide Range of Elastic Moduli2.3 Prediction of ViscoelasticityConclusions and Outlook