TY - JOUR
T1 - Synthesis and Characterization of Amorphous Bibenzoate (Co)polyesters
T2 - Permeability and Rheological Performance
AU - Mondschein, Ryan J.
AU - Dennis, Joseph M.
AU - Liu, Haoyu
AU - Ramakrishnan, Ramesh K.
AU - Nazarenko, Sergei
AU - Turner, S. Richard
AU - Long, Timothy E.
PY - 2017/10/10
Y1 - 2017/10/10
N2 - Melt polycondensation of bibenzoate dimethyl esters with ethylene glycol enabled the synthesis of polyesters containing linear (4,4′-bibenzoate (4,4′BB)) and kinked (3,4′-bibenzoate (3,4′BB)) repeating units. Novel 3,4′BB:4,4′BB (co)polyesters with ethylene glycol (EG) showed an onset of weight loss (Td,5%) above 350 °C. 1H NMR spectroscopy confirmed 4,4′BB:3,4′BB incorporation, and size exclusion chromatography (SEC) revealed high molecular weights. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) revealed glass transition temperatures (Tg) approaching 121 °C, crystallization and melting transition temperatures (Tc and Tm), and sub-Tg β-relaxations. 4,4′BB incorporation below ∼45 mol % afforded an amorphous morphology, while 4,4′BB incorporation above 45 mol % induced crystallinity. Melt rheology elucidated the effect of structure on flow behavior, and time-temperature superposition (TTS) revealed distinct flow transitions. TTS analysis also provided insight into the structural influence of regioisomers on fractional free volume (fg) and flow activation energies (Ea). Incorporation of the symmetrical 4,4′BB monomer negligibly affected the fg but imparted a stiffer overall chain, resulting in higher Ea. Positron annihilation lifetime spectroscopy (PALS) of the (co)polyesters confirmed a lack of change in free volume through measuring the average free volume of a spherical hole. Determination of oxygen permeability offered fundamental understanding of the relationship of monomer symmetry with gas permeability and free volume in unoriented films; kinked 3,4′BB monomer afforded higher overall barrier in amorphous films. Finally, tensile testing elucidated Young's moduli and yield strengths, confirming (co)polyesters' mechanical similarity to BPA-polycarbonate. Moduli ≤2.7 GPa and yield strengths up to 74 MPa confirmed BB-based (co)polyesters enhanced properties compared to other high-Tg polyesters.
AB - Melt polycondensation of bibenzoate dimethyl esters with ethylene glycol enabled the synthesis of polyesters containing linear (4,4′-bibenzoate (4,4′BB)) and kinked (3,4′-bibenzoate (3,4′BB)) repeating units. Novel 3,4′BB:4,4′BB (co)polyesters with ethylene glycol (EG) showed an onset of weight loss (Td,5%) above 350 °C. 1H NMR spectroscopy confirmed 4,4′BB:3,4′BB incorporation, and size exclusion chromatography (SEC) revealed high molecular weights. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) revealed glass transition temperatures (Tg) approaching 121 °C, crystallization and melting transition temperatures (Tc and Tm), and sub-Tg β-relaxations. 4,4′BB incorporation below ∼45 mol % afforded an amorphous morphology, while 4,4′BB incorporation above 45 mol % induced crystallinity. Melt rheology elucidated the effect of structure on flow behavior, and time-temperature superposition (TTS) revealed distinct flow transitions. TTS analysis also provided insight into the structural influence of regioisomers on fractional free volume (fg) and flow activation energies (Ea). Incorporation of the symmetrical 4,4′BB monomer negligibly affected the fg but imparted a stiffer overall chain, resulting in higher Ea. Positron annihilation lifetime spectroscopy (PALS) of the (co)polyesters confirmed a lack of change in free volume through measuring the average free volume of a spherical hole. Determination of oxygen permeability offered fundamental understanding of the relationship of monomer symmetry with gas permeability and free volume in unoriented films; kinked 3,4′BB monomer afforded higher overall barrier in amorphous films. Finally, tensile testing elucidated Young's moduli and yield strengths, confirming (co)polyesters' mechanical similarity to BPA-polycarbonate. Moduli ≤2.7 GPa and yield strengths up to 74 MPa confirmed BB-based (co)polyesters enhanced properties compared to other high-Tg polyesters.
UR - http://www.scopus.com/inward/record.url?scp=85031014182&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85031014182&partnerID=8YFLogxK
U2 - 10.1021/acs.macromol.7b01595
DO - 10.1021/acs.macromol.7b01595
M3 - Article
AN - SCOPUS:85031014182
SN - 0024-9297
VL - 50
SP - 7603
EP - 7610
JO - Macromolecules
JF - Macromolecules
IS - 19
ER -