Photo-Induced Reversible Deformation of Liquid Metal/Azo Polymer Hybrid Nanospheres for Application as Transformable Nanomachine

Liquid metal can be used in transformable soft robots due to its ability to manifest universal deformation effects under external field stimuli. However, the reversible transformation of liquid metals between different forms under the control of light fields has not been sufficiently investigated. In this work, a method to coat liquid metal nanodroplets with an azo polymer that exhibits photo-induced deformation properties has been developed. The azo polymer corona surrounding the liquid metal nanodroplets imparts the photo-induced deformation properties to the liquid metal. By alternating illumination to the liquid metal/azo polymer hybrid nanospheres with 488 nm polarized light and 980 nm light, the nanospheres can undergo a reversible transformation between spheres and ellipsoids. The interaction between liquid metal nanodroplets and the azo polymer shell is investigated by using density functional theory. This photo-induced reversible deformation successfully overcomes the limitations of the liquid metal itself in responding to external light stimuli, providing potential application as transformable nanomachine

Fabrication of Photoprocessible Azo Polymer Microwires through a Soft Lithographic Approach

In this work, a soft lithographic approach has been developed to fabricate free-standing azo polymer microwires with unique photoprocessible characteristics. In the process, an epoxy-based azo polymer (BP-AZ-CA) was used to prepare both the soft lithographic masters and the microwires. The masters were prepared by photofabricating surface relief gratings on BP-AZ-CA thin films. Then the elastomeric stamps were prepared by replica molding of poly(dimethylsiloxane) prepolymer against the masters. With use of the stamps and a solution of BP-AZ-CA as “ink”, the microwires were prepared by contact printing and wet etching. The microwires possessed a uniform sub-micrometer-scale transverse dimension and macroscopic longitudinal dimension. Those characteristic sizes depended on the adjustable features of the masters and stamps used in the process. The transverse dimension of the microwires could be altered after exposure to a linearly polarized Ar+ laser single beam with the polarization direction perpendicular to the longitudinal axes of the microwires. Upon irradiation of interfering p-polarized Ar+ laser beams, regular surface relief structures could be inscribed on the microwires along the longitudinal direction, which coincided with both the polarization direction of the laser beams and the grating vector direction of the interference pattern. The microwires with photoprocessible properties are potentially usable as sub-micrometer-scale materials in future miniaturized components and devices. The approach reported in this work can be further extended to the fabrication of nano-/microwires from other polymeric materials

Formation of Ordered Mesoporous Films from In situ Structure Inversion of Azo Polymer Colloidal Arrays

This work shows that mesoporous polymeric films with spherical and elliptical pores can be obtained by in situ structure inversion of the azo polymer colloid arrays through selective interaction with solvent. The epoxy-based azo polymer contained both the pseudo-stilbene-type azo chromophores and the hydrophilic carboxyl groups. The colloidal spheres of the azo polymer were prepared by gradual hydrophobic aggregation of the polymeric chains in THF−H2O media, induced by a steady increase in the water content. Ordered 2D arrays of the hexagonally close-packed colloidal spheres were obtained by the vertical deposition method. After the solvent (THF) annealing, the ordered 2D arrays were directly transformed to mesoporous films through the sphere−pore inversion. Under the same condition, the 2D arrays composed of the ellipsoidal colloids, which were obtained by the irradiation of a polarized Ar+ laser beam on the colloidal sphere arrays, could be transformed to films with ordered elliptical pores. To our knowledge, this is the first example to demonstrate that mesoporous structures can be directly formed from the colloidal arrays of a homopolymer through structure inversion. This observation can shed new light on the nature of self-assembly processes and provide a feasible approach to fabricate mesoporous structures without the infiltration−removal step. By exploring the photoresponsive properties of the materials, mesoporous film with special pore structure and properties can be expected

Hybrid Colloids Composed of Two Amphiphilic Azo Polymers: Fabrication, Characterization, and Photoresponsive Properties

This article reports the fabrication and characterization of a novel type photoresponsive colloids composed of two amphiphilic azo polymers. The colloids were built up by using an amphiphilic random azo copolymer (PEAPE) and a polydispersed azo homopolymer (BP-AZ-CA), which were functionalized with azobenzene type and pseudo-stilbene type chromophores, respectively. The colloids were prepared by gradually adding deionized water into a THF solution containing both PEAPE and BP-AZ-CA. In order to study the influence of the preparation conditions on the colloid composition and structure, the colloids were also prepared by mixing two THF−H2O solutions or dispersions of the polymers with different initial water content (Cw0) and then adding water into the mixture. When mixing the solutions with Cw0 below the critical water content (CWC), uniform colloidal spheres composed of the two polymers could be obtained. Upon irradiation of a linearly polarized Ar+ laser beam, the hybrid colloidal spheres were deformed to “tadpole-like”, “spindle-like”, and other nonspherical structures depending on the composition of the colloids. As only the BP-AZ-CA component could be driven by the light irradiation, the photoinduced deformation degree increased with the increase of the active component in the hybrid colloids. When mixing the dispersions with Cw0 above CWC, the colloids obtained were observed to be a mixture of the hybrid colloids and monocomponent colloids. The photoisomerization study confirmed that the cores of the hybrid colloids were formed from the more hydrophobic PEAPE component, and the coronas were rich in the BP-AZ-CA component. The colloidal structures were formed due to the gradual hydrophobic aggregation of the polymeric chains in the THF-H2O media. In the forming process, the more hydrophobic PEAPE chains started to aggregate first and then BP-AZ-CA chains gradually assembled on the cores while the water content gradually increased. The understanding and methodology can be applied to construct colloids composed of two or more photoresponsive polymers or even other functional polymers

Azo Polymer Microspherical Cap Array: Soft-Lithographic Fabrication and Photoinduced Shape Deformation Behavior

In this work, azo polymer microspherical cap arrays possessing unique photoprocessible properties have been fabricated through a soft-lithographic contact printing approach. In the process, hexagonal polystyrene (PS) colloidal arrays, obtained by the vertical deposition method, were used as masters. Poly(dimethylsiloxane) (PDMS) stamps with aligned hemisphere air voids on the surfaces were obtained by casting the precursor against the colloidal arrays. By using the stamps and a solution of an epoxy-based azo polymer (BP-AZ-CA) as “ink”, the microspherical cap arrays were fabricated by pressing the “inked” surfaces against substrates. Uniform 2D arrays of the submicrometer spherical caps could be obtained on the substrates after peeling off the stamps and drying. The characteristic sizes of the arrays depended on some adjustable features, such as the diameters of PS spheres and concentrations of the “inks” used in the process. After exposure to a linearly polarized Ar+ laser single beam, the spherical caps could be stretched along the polarization direction, and the arrays were consequently transformed into ellipsoidal cap arrays. Upon irradiation of interfering p-polarized Ar+ laser beams, only the spherical caps in the bright fringes were deformed by the light irradiation, which resulted in more complicated surface relief patterns. The observation gives another well-defined example of the photoinduced mass migration in the submicrometer scale. The approach can potentially be applied to fabrication of microlens arrays with different converging rate in two directions

Sequentially Adsorbed Electrostatic Multilayers of Branched Side-Chain Polyelectrolytes Bearing Donor−Acceptor Type Azo Chromophores

Two newly synthesized polyelectrolytes (PBANT-AC and PBACT-AC) functionalized with branched side chains bearing electron donor−acceptor type azobenzene chromophores were used as polyanions to build up multilayer films through an electrostatic sequential adsorption process by using poly(diallyldimethylammonium chloride) (PDAC) as the polycation. When dissolved in anhydrous DMF and a series of DMF−H2O mixed solvents with different DMF to H2O ratios, both azo polyelectrolytes could form uniform multilayer films through the layer-by-layer adsorption process. Altering the water content of the dipping solutions of both azo polyelectrolytes was found to dramatically change the thickness of the sequentially adsorbed bilayers, chromophore orientation, and surface roughness of the multilayer films. On the other hand, the solvent effect on the H-aggregation in the multilayer films was determined by the structural details of the azo polyelectrolytes. After the irradiation with a linearly polarized Ar+ laser beam at 488 nm, significant dichroism was induced in the PBANT-AC/PDAC multilayer films prepared from the DMF dipping solution. Upon exposure to an interference pattern of Ar+ laser beam at modest intensities, optically induced surface modulation on the multilayer surfaces was observed

Synthesis, liquid crystalline mesophases and morphologies of diblock copolymers composed of a poly(dimethylsiloxane) block and a nematic liquid crystalline block

<p>In this study, a series of liquid crystalline diblock copolymers, composed of a soft poly(dimethylsiloxane) (PDMS) block with a defined length and a side-on liquid crystalline poly(3ʹʹ-acryloyloxypropyl 2,5-di(4ʹ-butyloxybenzoyloxy) benzoate) (P3ADBB) block with different lengths, are synthesised by the atom transfer radical polymerisation. The macromolecular structures, liquid crystalline properties and the microphase-separated morphologies of the diblock copolymer are investigated by ¹H NMR, FT-IR, GPC, POM, DSC and TEM. The results show that the well-defined diblock copolymers (PDMS_n-<i>b</i>-P3ADBB_m) possess four different soft/rigid ratios (<i>n</i> = 58, <i>m</i> = 10, 25, 42, 66) and relatively narrow molecular distributions (PDI ≤ 1.30). P3ADBB blocks of the copolymers show nematic sub-phases, which are identical to the mesomorphic behaviour of the homopolymer P3ADBB. After being annealed at 90°C in a vacuum oven for 48 h, the copolymers form a lamellar morphology when <i>m</i> = 10 and morphologies of PDMS spheres embedded in P3ADBB matrix when <i>m</i> = 25, 42 and 66.</p

Photoinduced Deformation of Amphiphilic Azo Polymer Colloidal Spheres

Photoinduced shape deformation of colloidal spheres made of an amphiphilic azo polymer has been demonstrated in this work. The polymer contains the donor-and-acceptor-type azobenzene chromophores and can form uniform colloidal spheres by dropwise adding water into its THF solution. When the colloidal spheres obtained were exposed to the interfering p-polarized Ar+ laser beams (150 mW/cm2), the colloidal spheres changed to prolates (i.e., “rugby-balls”), “spindles”, and finally “rods”, depending on the irradiation times. The elongated direction of the spheres was observed to be the same as the polarization direction of the laser beam. The average major-to-minor ratio of the ellipsoids could be easily adjusted by controlling the irradiation time. The deformation effect observed in this work can offer a new way to prepare nonspherical colloids from colloidal spheres and will shed new light on the correlation between the photodriven shape deformation and photoinduced surface relief gratings for the same type of polymers

Elevated Levels of Serum Tumor Markers CEA and CA15-3 Are Prognostic Parameters for Different Molecular Subtypes of Breast Cancer

<div><p>Background & Aims</p><p>The utility of measuring carcinoembryonic antigen(CEA) and cancer antigen 15-3 (CA15-3) levels in patients with breast cancer remains controversial. The present study aims to investigate the prognostic value of preoperative serum CEA and CA15-3 levels in breast cancer patients.</p><p>Methods</p><p>Serum preoperative CEA and CA 15-3 concentration levels were measured in a total of 432 breast cancer patients. The association of tumor markers levels with clinicopathological parameters and outcomes were analyzed.</p><p>Results</p><p>Elevated serum levels of CEA and CA15-3 were identified in 47 (10.9%) and 60(13.9%) patients, respectively. Larger tumor size, advanced axillary lymph nodal and TNM stage exhibited higher proportion of elevated CEA and CA15-3 levels. The elevation of CEA levels was significantly greater in patients with HER2 positive tumors, and the elevation of CA15-3 levels was significantly greater in ER negative breast patients. Univariate and multivariate Cox’s regression analysis revealed that elevated preoperative CEA and CA 15-3 levels were independent prognostic factors for DFS and OS. When considering the combination of both markers levels, patients with both elevated markers presented the worst survival. Independent prognostic significance of elevated preoperative serum CEA and CA15-3 levels were reconfirmed in Luminal B breast cancer.</p><p>Conclusions</p><p>Preoperative serum levels of CEA and CA15-3 are independent prognostic parameters for breast cancer.</p></div

Azo Coupling Reaction Induced Macromolecular Self-Assembly in Aqueous Solution

This communication reported azo coupling reaction induced macromolecular self-assembly in aqueous solution. Diblock copolymer (PEG-<i>b</i>-PSNHBoc) consisting of a hydrophilic PEG block, and a hydrophobic N-Boc protected poly­(<i>p</i>-vinylaniline) block was synthesized by RAFT polymerization. Then double hydrophilic diblock copolymer (PEG-<i>b</i>-PSN₂⁺) composed of PEG and PS based macromolecular diazonium salts was prepared by the diazotization of PEG-<i>b</i>-PSNH₂, which was obtained by deprotection of PEG-<i>b</i>-PSNHBoc. As <i>N</i>,<i>N</i>-dimethylaniline was gradually added into the freshly prepared PEG-<i>b</i>-PSN₂⁺ aqueous solution, the azo coupling reaction between <i>N</i>,<i>N</i>-dimethylaniline and diazonium salts took place, which would lead to the generation of azobenzene pendants. Due to the poor solubility of azobenzene pendants in water, the formed hydrophobic polymeric chains aggregated to form the self-assembly colloidal particles. By incorporating a fluorescent group into the aniline, the aggregates formed through azo coupling reaction induced macromolecular self-assembly showed enzyme-triggered fluorescent behaviors