Biomaterials are indispensable elements for improving human health and quality of life. Applications of biomaterials include the use of phantoms as tissue replacement in diagnostics (biosensors), medical supplies (blood bags and surgical instruments), therapeutic treatments (medical implants and devices), regenerative medicine (tissue engineered skin and cartilage), and radiation dosimetric studies. Since polymers are organic, they offer a much more versatile usage area than metals and ceramic biomaterials, particularly in soft tissue substitutes. The wide physical, mechanical, and chemical properties provided by polymers have encouraged extensive research, development, and application of polymeric biomaterials. Their usage as a soft tissue phantom is at the forefront of these applications. In this study, the ionization, recoils, phonon release, collision events, and lateral straggle properties of polymeric biomaterials [e.g., polymethylmetacrylate (PMMA), polystyrene, polyethylene, polypropylene, and polyvinylchloride] closest to soft tissue are investigated in carbon therapy application. The Brag peak location achieved for PMMA is quite close to that of soft tissue, within 4.8%, average recoils within 0.5%, and collision event parameter within 0.6%, however, lateral scattering is comparatively larger by roughly 6.8%, according to TRIM-based Monte Carlo simulation results. Thus, when carbon ion is taken into account, the current findings show that PMMA is one of the possible polymeric biomaterials to simulate soft tissue in terms of radiation interaction properties.