TY  - JOUR
A1  - Melchert, Christian
A1  - Yongvongsoontorn, Nunnarpas
A1  - Behl, Marc
A1  - Lendlein, Andreas
T1  - Synthesis and characterization of telechelic oligoethers with terminal cinnamylidene acetic acid moieties
JF  - Journal of applied biomaterials & functional materials
N2  - Purpose: The formation of photoresponsive hydrogels were reported by irradiation of star-shaped poly(ethylene glycol)s with terminal cinnamylidene acetic acid (CAA) groups, which are capable of a photoinduced [2+2] cycloaddition. In this study we explored whether oligo(ethylene glycol) s and oligo(propylene glycol)s of varying molecular architecture (linear or star-shaped) or molecular weights could be functionalized with CAA as terminal groups by esterification or by amide formation.
 Methods: Oligo(ethylene glycol) (OEG) and oligo(propylene glycol) (OPG) with varying molecular architecture (linear, star-shaped) and weight average molecular weights between 1000 and 5000 g.mol(-1) were functionalized by means of esterification of hydroxyl or amine endgroups with cinnamylidene acetic acid (CAA) or cinnamylidene acetyl chloride (CAC) as telechelic endgroups. The chemical structure, thermal properties, and molecular weights of the oligoethers obtained were determined by NMR spectroscopy, UV spectroscopy, DSC, and MALDI-TOF.
 Results: CAA-functionalized linear and star-shaped OEGs or OPGs could be obtained with a degree of functionalization higher than 90%. In MALDI-TOF measurements an increase in Mw of about 150 g.mol(-1) (for each terminal end) after the functionalization reaction was observed. OEGCAA and OPGCAA showed an increase in glass transition temperature (T-g) from about -70 degrees C to -50 degrees C, compared to the unfunctionalized oligoethers. In addition, the melting temperature (T-m) of OEGCAA decreased from about 55 C to 30 degrees C, which can be accounted for by the hampered crystallization of the precursors because of the bulky CAA end groups as well as by the loss of the hydroxyl telechelic end groups.
 Conclusion: The synthesis of photoresponsive oligoethers containing cinnamylidene acetic acid as telechelic endgroup was reported and high degrees of functionalization could be achieved. Such photosensitive oligomers are promising candidates as reactive precursors, for the preparation of biocompatible high molecular weight polymers and polymer networks.
KW  - Biocompatible polymers
KW  - Cinnamylidene acetic acid
KW  - Photoresponsive polymers
Y1  - 2012
U6  - https://doi.org/10.5301/JABFM.2012.10364
SN  - 2280-8000
VL  - 10
IS  - 3
SP  - 185
EP  - 190
PB  - Wichtig
CY  - Milano
ER  - 
TY  - JOUR
A1  - Melchert, Christian
A1  - Behl, Marc
A1  - Nöchel, Ulrich
A1  - Lendlein, Andreas
T1  - Influence of Comesogens on the Thermal and Actuation Properties of 2-tert-Butyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone Based Nematic Main-Chain Liquid Crystalline Elastomers
JF  - Macromolecular materials and engineering
N2  - Although the shape-changing capabilities of LCEs hold great potential for applications ranging from micropumps to artificial muscles, customization of the LCE functionality to the applications' requirements is still a challenge. It is studied whether the orientation of NMC-LCPs and NMC-LCEs based on 2-tert-butyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone can be enhanced by copolymerization with 2-methyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone or 2,6-bis[4-(4-pentenyl-oxy)-benzoyl]anthracene. An increasing content of the comonomers stabilizes the nematic phase, which enables a tailoring of T-NI for the NMC-LCP between 45 and 68 degrees C, while for the NMC-LCE T-NI ranges between 69 and 76 degrees C. In addition, NMC-LCE show an increased actuation performance.
KW  - elastomers
KW  - liquid-crystalline polymers
KW  - polysiloxanes
KW  - stimuli-sensitive polymers
KW  - thermal properties
Y1  - 2012
U6  - https://doi.org/10.1002/mame.201200238
SN  - 1438-7492
VL  - 297
IS  - 12
SP  - 1203
EP  - 1212
PB  - Wiley-VCH
CY  - Weinheim
ER  -