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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Z-E isomerization of azobenzene based amphiphilic poly(urethane-urea)s: Influence on the dynamic mechanical properties and the effect of the self-assembly in solution on the isomerization kinetics

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Santos Paiva, Germana Maria [1] ; Teixeira Alves Duarte, Luis Gustavo [1] ; Faleiros, Marcelo Meira [1] ; Zambon Atvars, Teresa Dib [1] ; Felisberti, Maria Isabel [1]
Total Authors: 5
[1] Univ Campinas R Josue de Castro, Inst Chem, POB 6154, BR-13084971 Campinas, SP - Brazil
Total Affiliations: 1
Document type: Journal article
Source: EUROPEAN POLYMER JOURNAL; v. 127, MAR 15 2020.
Web of Science Citations: 0

Azobenzene containing polymers have been used in the development of materials and devices responsive to light, devices for optical storage information, with shape-changing and shape-memory capacities, surface-relief grating, holograms, etc. Poly(urethane-urea)s (PUU) based on a hydrophilic polyethylene glycol (PEG-PUU), on a hydrophobic polycaprolactone diol (PCL-PUU) polyols, and on an equimolar mixture of them (PEG/PCL-PUU), 4,4'-diphenylmethane diisocyanate and 4,4'-diaminoazobenzene (DAAB), as a chain extender, were synthesized by a two-step route. PUU were characterized with respect to their chemical structure, molar masses, thermal and dynamic mechanical properties, and spectroscopic properties. The kinetics of the photo- and thermal-induced isomerization were studied in DMF solutions. The isomerization rate constant was two orders of magnitude higher for DAAB compared with PUU in DMF solution, except for PEG/PCL-PUU, for which the rate constant was half the value observed for DAAB. The amphiphilic nature of the PUU resulted in aggregates in DMF and, therefore, the azo isomerization for PEG-PUU and PCL-PUU occurred in a solid-state-like environment. On the other hand, PEG/PCL-PUU presented unimers and aggregates in DMF and the isomerization of azo groups in free PUU chains was faster. The PUU were semicrystalline and thermo-mechanically stable up 150 degrees C due to the hydrogen bonding involving urea, urethane and ester groups. The aggregates size in DMF solution, as well as the dynamic mechanical properties of the PUU, were sensitive to photo- and thermo-induced isomerization. (AU)

FAPESP's process: 15/25406-5 - Organizing matter: colloids formed by association of surfactants, polymers and nanoparticles
Grantee:Watson Loh
Support Opportunities: Research Projects - Thematic Grants
FAPESP's process: 16/11197-8 - Polyurethanes tri- and tetra blocks functionalized with azo group: synthesis, characterization and evaluation of potential as photo-responsive materials
Grantee:Germana Maria Santos Paiva
Support Opportunities: Scholarships in Brazil - Doctorate
FAPESP's process: 13/16245-2 - Photophysical properties of thin films of conjugated polymers
Grantee:Teresa Dib Zambon Atvars
Support Opportunities: Regular Research Grants