  In this paper, we continue the analysis of the effective model of quantum
Schwarzschild black holes recently proposed by some of the authors in [1,2]. In
the resulting spacetime the central singularity is resolved by a black-to-white
hole bounce, quantum effects become relevant at a unique mass independent
curvature scale, while they become negligible in the low curvature region near
the horizon and classical geometry is approached asymptotically. This is the
case independently of the relation between the black and white hole masses,
which are thus freely specifiable independent observables. A natural question
then arises about the phenomenological implications of the resulting
non-singular effective spacetime and whether some specific relation between the
masses can be singled out from a phenomenological perspective. Here we focus on
the thermodynamic properties of the effective polymer black hole and analyse
the corresponding quantum corrections as functions of black and white hole
masses. The study of the relevant thermodynamic quantities such as temperature,
specific heat and horizon entropy reveals that the effective spacetime
generically admits an extremal minimal-sized configuration of
quantum-gravitational nature characterised by vanishing temperature and
entropy. For large masses, the classically expected results are recovered at
leading order and quantum corrections are negligible, thus providing us with a
further consistency check of the model. The explicit form of the corrections
depends on the specific relation among the masses. In particular, a first-order
logarithmic correction to the entropy is obtained for a quadratic mass
relation. The latter corresponds to the case of proper finite length effects
which turn out to be compatible with a minimal length generalised uncertainty
principle associated with an extremal Planck-sized black hole.
