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1.
Chem Commun (Camb) ; 55(20): 2880-2891, 2019 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-30762048

RESUMO

Stimulus-responsive photonic polymer materials that change their reflection colour as function of environmental stimuli such as temperature, humidity and light, are attractive for various applications (e.g. sensors, smart windows and communication). Polymers provide low density, tunable and patternable materials. This feature article focusses on various autonomously responding photonic polymer materials such as hydrogels, block copolymers and liquid crystals and discusses their potential industrial implementation.

2.
Small ; 14(50): e1803274, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30353702

RESUMO

Light responsive materials that are able to change their shape are becoming increasingly important. However, preconfigurable bistable or even multi-stable visible light responsive coatings have not been reported yet. Such materials will require less energy to actuate and will have a longer lifetime. Here, it is shown that fluorinated azobenzenes can be used to create rewritable and pre-configurable responsive surfaces that show multi-stable topographies. These surface structures can be formed and removed by using low intensity green and blue light, respectively. Multistable preconfigured surface topographies can also be created in the absence of a mask. The method allows for full control over the surface structures as the topographical changes are directly linked to the molecular isomerization processes. Preliminary studies reveal that these light responsive materials are suitable as adaptive biological surfaces.

3.
Angew Chem Int Ed Engl ; 57(50): 16385-16390, 2018 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-30182453

RESUMO

Structural heterogeneity defines the properties of many functional polymers and it is often crucial for their performance and ability to withstand mechanical impact. Such heterogeneity, however, poses a tremendous challenge for characterization of these materials and limits our ability to design them rationally. Herein we present a practical methodology capable of resolving the complex mechanical behavior and tracking mechanical impact in discrete phases of segmented polyurethane-a typical example of a structurally complex polymer. Using direct optical imaging of photoluminescence produced by a small-molecule organometallic mechano-responsive sensor we observe in real time how polymer phases dissipate energy, restructure, and breakdown upon mechanical impact. Owing to its simplicity and robustness, this method has potential in describing the evolution of complex soft-matter systems for which global characterization techniques fall short of providing molecular-level insight.

4.
ChemSusChem ; 11(1): 149-158, 2018 01 10.
Artigo em Inglês | MEDLINE | ID: mdl-29116685

RESUMO

Here, an isocyanate-free approach to produce polyureas from diamines and dicarbamates as monomers is reported. A side reaction limiting the molecular weight during the diamine/ dicarbamate polymerization, that is, N-alkylation of amine end groups, is investigated. Mitigation of the N-alkylation, either by enhancing the carbamate aminolysis rate or by substitution of dimethylcarbamates with more sterically hindered diethylcarbamates, affords polyureas with sufficiently high molecular weights to assure satisfactory mechanical properties. Stable polyurea dispersions with polyamines as internal dispersing agents are prepared, and the properties of the corresponding coatings are evaluated.


Assuntos
Polímeros/síntese química , Água/química , Alquilação , Carbamatos/química , Diaminas/química , Isocianatos/química , Peso Molecular , Polimerização , Polímeros/química
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