Facile Synthesis, Large Optical Nonlinearity, and Excellent Thermal Stability of Hyperbranched Poly(aryleneethynylene)s Containing Azobenzene Chromophores

Dendronized Hyperbranched Polymer: A New Architecture for Second-Order Nonlinear Optics

Organic/polymeric second-order nonlinear optical (NLO) materials, which rely on the poling-induced non-centrosymmetric arrangement of NLO chromophores, have played a very important role in laser technology and optical fiber communication, due to their ultra-fast response speed, excellent machining performance and low dielectric constant. However, the NLO chromophores have the large dipole moments with strong intramolecular charge transfer, which lead to the intermolecular electrostatic interactions to tend to the centrosymmetric arrangement and decrease the poling efficiency. Since the special three-dimensional spatial separation can minimize these strong intermolecular electrostatic interactions during poling process, dendrimers and hyperbranched polymers have been considered as better topology for the next generation of highly efficient NLO materials. In 2013, by the attachment of low generation dendrimers to the hyperbranched backbone, a new dendritic architecture of dendronized hyperbranched polymer (DHP) was proposed for improving the comprehensive performance of NLO materials. Recent results showed many advantages of DHPs in NLO field, such as easy syntheses, large NLO coefficients and high orientation stability, etc. In this review, the latest advancement of DHPs, including the design principle, synthesis, as well as their application as NLO materials is summarized. The new opportunities arising from DHPs are also summarized in the future perspective.

Hyperbranched Macromolecules: From Synthesis to Applications

Hyperbranched macromolecules (HMs, also called hyperbranched polymers) are highly branched three-dimensional (3D) structures in which all bonds converge to a focal point or core, and which have a multiplicity of reactive chain-ends. This review summarizes major types of synthetic strategies exploited to produce HMs, including the step-growth polycondensation, the self-condensing vinyl polymerization and ring opening polymerization. Compared to linear analogues, the globular and dendritic architectures of HMs endow new characteristics, such as abundant functional groups, intramolecular cavities, low viscosity, and high solubility. After discussing the general concepts, synthesis, and properties, various applications of HMs are also covered. HMs continue being materials for topical interest, and thus this review offers both concise summary for those new to the topic and for those with more experience in the field of HMs.

Rationally designed hyperbranched azopolymer with temperature, photo and pH responsive behavior

A novel hyperbranched azopolymer, HPAzoAMAM-star-EG₃, was synthesized and it could self-assemble into uniform large compound micelles with multi-stimuli responsive behavior.

Theoretical study of the spectroscopic and nonlinear optical properties of trans- and cis-4-hydroxyazobenzene

We investigate the molecular structure, vibrational and electronic absorption spectra, and electronic hyperpolarizabilities of trans and cis isomers of 4-hydroxyazobenzene (HOAB) via density functional theory. Results show that the azo dye exhibits a high third-order nonlinear optical response and good optical transparency. Both the basis set and the functional are important influences on the results obtained when calculating the absorption spectrum and NLO response. We also study the effect of the solvent on the electronic absorption spectrum to assess the ability of the functional to reproduce the experimental spectrum in combination with a suitable solvent model. Our calculations show that the SMD model of Truhlar et al. handles the electrostatic and the non-electrostatic effects of hydrogen-bonding solvents on the absorption spectrum better than the traditional polarizable continuum model does. In addition, our results indicate that the dye trans-HOAB exhibits a high second hyperpolarizability and excellent optical transparency. Also, although the second hyperpolarizability of cis-HOAB is much lower than that of trans-HOAB, it is non-negligible when calculating the optical nonlinearity of HOAB under an optical pump. We also examine the effect of frequency dispersion on second harmonic generation. This study provides the basis for further research on the spectroscopic and nonlinear optical properties of novel azo dyes and other π-conjugated compounds.

Synthesis and characterization of visible-light-activated Azo hyperbranched polymers

All visible-light-activated Azo polymer photoswitches were efficiently synthesized via combination of the AuNP-catalyzed photocatalytic method and the A₃ monomer strategy.

Development of a transition metal-free polymerization route to functional conjugated polydiynes from a haloalkyne-based organic reaction

Construction of functional polydiynes by transition metal-free homo-polycoupling of bis(iodoalkyne)s.

Synthesis, Self-Assembly, and Photoresponsive Behavior of Tadpole-Shaped Azobenzene Polymers

Herein, we report a feasible method to prepare a tadpole-shaped PEG-POSS-(Azo)₇ polymer. The polymer self-assembled into a large vesicle in aqueous solution, undergoing reversible smooth-curling transformation responsive to UV and dark conditions. Incorporating POSS units into the azopolymer furnished quick trans-cis isomerization along a cubic orientation. The orientational isomerization formed some pores on the vesicular membrane and endowed the highly sensitive photoresponsive property. Encapsulation of various fluorescent dyes affected the hydrophilic/hydrophobic ratio of self-assemblies, causing their morphological transition from vesicles to micelles. Response to UV irradiation, the quick trans-cis isomerization resulted in rapid release of the encapsulated dyes. The intriguing photoresponsive property renders this kind of tadpole-shaped POSS hybrid azopolymer a potential for application in controlled release of drug.

Hyperbranched polymers: advances from synthesis to applications

This review summarizes the advances in hyperbranched polymers from the viewpoint of structure, click synthesis and functionalization towards their applications in the last decade.

Functional hyperbranched polymers with advanced optical, electrical and magnetic properties

This review summarizes the recent progress in functional HBPs and their application in optics, electronics and magnetics, including light-emitting devices, aggregation-induced emission materials, nonlinear optical materials, chemosensors, solar cells, magnetic materials, etc., and provides outlooks for further exploration in the field.

Photoresponsive smectic liquid crystalline multipods and hyperbranched azo polymers

Liquid crystalline azobenzene containing triped and tetraped monomers were designed and synthesized and further used as B3 and B4 type monomers to form hyperbranched polymers with tetraethylene glycol as the A2 type comonomer. The mesophase characteristics of the multiarm-star mesogens and hyperbranched polymers were analyzed using various instrumentation techniques like differential scanning calorimetry (DSC), polarized light microscopy (PLM) and variable temperature XRD. The multipod monomers as well as hyperbranched polymers exhibited thermotropic smectic liquid crystalline characteristics with a tendency toward higher ordered smectic LC phases with increased branching. The hyperbranched polymers exhibited lamellar organization even in the as-solvent precipitated powder sample indicating higher extent of nanosegregation. Their potential application as fast switching photochromic materials was highlighted by carrying out isothermal photoswitching experiments in the LC state. Reversible isothermal smectic-isotropic phase transition could be achieved by UV irradiation in <1 s in the multipod monomers, while it required >2 s UV irradiation in the case of the hyperbranched polymers.

From nitro- to sulfonyl-based chromophores: improvement of the comprehensive performance of nonlinear optical dendrimers

Through the combination of the divergent and convergent approaches, coupled with the utilization of the powerful Sharpless "click-chemistry" reaction, two series of sulfonyl-based high-generation NLO dendrimers were conveniently prepared with high purity and in satisfactory yields. Thanks to the perfect three-dimensional (3D) spatial isolation from the highly branched structure and the isolation effect of the exterior benzene moieties and the interior triazole rings, these dendrimers exhibited large second harmonic generation coefficient (d33) values up to 181 pm V(-1), which, to the best of our knowledge, is the highest value so far for polymers containing sulfonyl-based chromophore moieties. Meanwhile, compared with the nitro-chromophore-based analogues, their optical transparency and NLO stability were improved in a large degree, due to the lower dipole moment (μ) and the special main-chain structure of sulfonyl-based chromophore in these dendrimers.

Synthesis and nonlinear optical properties of a peripherally functionalized hyperbranched polymer by DR1 chromophores

The first peripheral postfunctionalization of a hyperbranched polyimide by nonlinear optic chromophores (DR1 derivative) was achieved using two different routes. The first one consists in the esterification of the terminal carboxylic acid groups, whereas the second is based on copper-catalyzed Huisgen reaction of the terminal propargylic ester groups. The resulting polymers display good solubility in classical organic solvents and good filmability because thick films can be prepared (up to 2.7 mum). The second-order nonlinear optical properties were measured by SHG at 1064 nm and we show that these hyperbranched polymers exhibit good poling efficiency and good thermal stability since the electro-optic activity remains stable up to 130 degrees C. These results illustrate the potential of hyperbranched polymers to host second-order nonlinear optical chromophores to replace dendrimers or classical linear polymers generally used in this area.