  The incredible thermo-mechanical properties of biological materials arise
from the microscopic scale due to a complex hierarchical mechanism, regulated
by microinstabilities at the molecular level. The description of such complex
structures is allowed by both the know-how introduced by the advent of SMFS
experiments and the possibility of correctly mimicking their behaviour at the
lowest scales. In this thesis, different classes of models with non
convex-energies are introduced to describe the important features of phase
transition, decohesion and damage under different conditions of applied forces
and displacement, thermal fields and rates of loading. Moreover, within a
Statistical Mechanics framework, temperature effects are considered also
including the rate of loading. Different phenomena have been analyzed such as
the effect of the handling device in protein unfolding, the nucleation and
generation of phase interfaces in nanowires or the cooperativity of weak
interactions in double stranded chains, as in the case of the DNA or the
bundles of microtubules and tau proteins inside the neuronal axons. The results
obtained in the thesis are compared to pieces of evidence from an extensive
literature review and to the experimental behaviours of the systems described.
