Objectives. This research investigated the dynamic mechanical properti
es of two model dental restorative copolymers to elucidate the influen
ce of pendent group length and addition of crosslinking agent. Methods
. Two different monomethacrylate resins [(methyl methacrylate (MMA) or
2-ethoxyethylmethacrylate (EEM)] were added to Various molar fraction
s (0, 5, 10, 20, 40, 60, 80 and 100%) of a difunctional monomer [triet
hylene glycol dimethacrylate (TEGDMA)], resulting in two different cop
olymer systems (TMMA and TEEM). Bar-shaped specimens were heat-cured a
nd tested for their dynamic mechanical properties at a fixed frequency
(1 Hz): flexural storage modulus and loss factor. Transition temperat
ures associated with peaks were determined using tan delta, phase angl
e and loss factor. The properties of one specimen were also examined u
sing a range of applied frequencies. Results. Below the Tg, all resin
systems had similar storage moduli. An increase in pendent group lengt
h lowered transition temperatures and demonstrated greater influence o
n temperature changes than did a change in crosslinker content. With i
ncreasing crosslinker, the transition temperatures increased. The valu
es ascribed to transition temperatures were dependent upon the analysi
s method used: tan delta gave highest values, followed by phase angle,
with loss factor values the lowest. Storage and loss moduli values an
d their ratio increased with increasing frequency of applied signal. L
oss factor analysis provided the most elucidation of sub-Tg transition
s. Significance. Restorative polymers with specific desired physical a
nd mechanical properties can be achieved by both judicious selection o
f monomer structure as well as by the controlled addition of the cross
linking agent.