Proses Produksi Dan Pengemasan Yoghurtdicv. Cita Nasional Salatiga

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Two-Dimensional Supramolecular Assemblies from pH-Responsive Poly(ethyl glycol)‑<i>b</i>‑poly(l‑glutamic acid)‑<i>b</i>‑poly(<i>N</i>‑octylglycine) Triblock Copolymer

Amphiphilic block copolymers containing polypeptides can self-assemble into a variety of nonspherical structures arising from strong interactions between peptide units. Here, we report the synthesis of a pH-responsive poly­(ethyl glycol)-<i>block</i>-poly­(l-glutamic acid)-<i>block</i>-poly­(<i>N</i>-octylglycine) (PEG-<i>b</i>-PGA-<i>b</i>-PNOG) triblock copolymers by sequential ring-opening polymerization using amine-terminated poly­(ethyl glycol) as the macroinitiator followed by selective deprotection of the benzyl protecting group. The obtained triblock copolymer can be directly dispersed in aqueous solution with hydrophilic PEG, pH-responsive PGA block, and hydrophobic PNOG. We present a systematic study of the influence of pH, molar fraction, and molecular weight on the self-assemblies. It was found that the PEG-<i>b</i>-PGA-<i>b</i>-PNOG triblock tends to form two-dimensional nanodisks and nanosheet-like assemblies. The nanodisk-to-nanosheet transition is highly dependent on the pH and molar fraction despite the different molecular weights. We demonstrate that the dominant driving force of the nanodisks and nanosheets is the hydrophobicity of the PNOG blocks. The obtained bioinspired 2D nanostructures are potential candidates for applications in nanoscience and biomedicine

Controlling the Structure and Morphology of Organic Nanofilaments Using External Stimuli

In our continuing pursuit to generate, understand, and control the morphology of organic nanofilaments formed by molecules with a bent molecular shape, we here report on two bent-core molecules specifically designed to permit a phase or morphology change upon exposure to an applied electric field or irradiation with UV light. To trigger a response to an applied electric field, conformationally rigid chiral (S,S)-2,3-difluorooctyloxy side chains were introduced, and to cause a response to UV light, an azobenzene core was incorporated into one of the arms of the rigid bent core. The phase behavior as well as structure and morphology of the formed phases and nanofilaments were analyzed using differential scanning calorimetry, cross-polarized optical microscopy, circular dichroism spectropolarimetry, scanning and transmission electron microscopy, UV–vis spectrophotometry, as well as X-ray diffraction experiments. Both bent-core molecules were characterized by the coexistence of two nanoscale morphologies, specifically helical nanofilaments (HNFs) and layered nanocylinders, prior to exposure to an external stimulus and independent of the cooling rate from the isotropic liquid. The application of an electric field triggers the disappearance of crystalline nanofilaments and instead leads to the formation of a tilted smectic liquid crystal phase for the material featuring chiral difluorinated side chains, whereas irradiation with UV light results in the disappearance of the nanocylinders and the sole formation of HNFs for the azobenzene-containing material. Combined results of this experimental study reveal that in addition to controlling the rate of cooling, applied electric fields and UV irradiation can be used to expand the toolkit for structural and morphological control of suitably designed bent-core molecule-based structures at the nanoscale

Metal–Organic Frameworks for Electrocatalytic Reduction of Carbon Dioxide

A key challenge in the field of electrochemical carbon dioxide reduction is the design of catalytic materials featuring high product selectivity, stability, and a composition of earth-abundant elements. In this work, we introduce thin films of nanosized metal–organic frameworks (MOFs) as atomically defined and nanoscopic materials that function as catalysts for the efficient and selective reduction of carbon dioxide to carbon monoxide in aqueous electrolytes. Detailed examination of a cobalt–porphyrin MOF, Al₂(OH)₂TCPP-Co (TCPP-H₂ = 4,4′,4″,4‴-(porphyrin-5,10,15,20-tetrayl)­tetrabenzoate) revealed a selectivity for CO production in excess of 76% and stability over 7 h with a per-site turnover number (TON) of 1400. In situ spectroelectrochemical measurements provided insights into the cobalt oxidation state during the course of reaction and showed that the majority of catalytic centers in this MOF are redox-accessible where Co­(II) is reduced to Co­(I) during catalysis

Probing and Controlling Liquid Crystal Helical Nanofilaments

We report the first in situ measurement of the helical pitch of the helical nanofilament B4 phase of bent-core liquid crystals using linearly polarized, resonant soft X-ray scattering at the carbon K-edge. A strong, anisotropic scattering peak corresponding to the half-pitch of the twisted smectic layer structure was observed. The equilibrium helical half-pitch of NOBOW is found to be 120 nm, essentially independent of temperature. However, the helical pitch can be tuned by mixing guest organic molecules with the bent-core host, followed by thermal annealing

Synthesis and Photovoltaic Properties of a Series of Narrow Bandgap Organic Semiconductor Acceptors with Their Absorption Edge Reaching 900 nm

Three <i>n</i>-OS acceptors with <i>E</i>_g values of <1.4 eV were synthesized by introducing double-bond π-bridges into ITIC (ITVIC) and ITIC with monofluorine (ITVfIC) or bifluorine (ITVffIC) substituents on its end groups, and the structure–property relationships of the acceptors were systematically studied. The three <i>n</i>-OS films show broad absorption covering the wavelength range of 550–900 nm with narrow <i>E</i>_g values of 1.40 eV for ITVIC, 1.37 eV for ITVfIC, and 1.35 eV for ITVffIC. Additionally, the fluorine substitution downshifted the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the compounds. The photovoltaic properties of the <i>n</i>-OS acceptors were investigated by using a medium bandgap conjugated polymer J71 as a donor. The optimized polymer solar cells (PSCs) based on J71:ITVffIC demonstrated a power conversion efficiency (PCE) of 10.54% with a high <i>J</i>_sc of 20.60 mA cm^–2 and a <i>V</i>_oc of 0.81 V, and the highest <i>J</i>_sc reached 22.83 mA cm^–2. The high <i>J</i>_sc values of the devices could be attributed to the broad absorption and lower-lying HOMO energy levels of the acceptor. Considering the <i>V</i>_oc of 0.81 V and the narrow bandgap of 1.35 eV for the acceptor ITVffIC, we found the energy loss (<i>E</i>_loss) of the ITVffIC-based PSCs was reduced to 0.54 eV, which is the lowest value in the PSCs with a PCE of >10%. The results indicate that ITVffIC is a promising narrow <i>E</i>_g acceptor for application in tandem and semitransparent PSCs

Effect of Side-Chain Engineering of Bithienylbenzodithiophene-<i>alt</i>-fluorobenzotriazole-Based Copolymers on the Thermal Stability and Photovoltaic Performance of Polymer Solar Cells

Side-chain engineering of conjugated polymer donor materials is an important way for improving photovoltaic performances of polymer solar cells (PSCs). On the basis of the polymer J61 synthesized in our group, here, we design and synthesize three new 2D-conjugated polymers J62, J63, and J64 with different types of side chains to further investigate the effect of side chain on their physicochemical and photovoltaic properties. With the narrow bandgap n-type organic semiconductor (n-OS) ITIC as acceptor, the optimized PSCs based on polymer donor of J62 with linear octyl, J63 with linear unsaturated hexylene, and J64 with cyclohexane side chains display power conversion efficiency (PCE) of 10.81%, 8.13%, and 8.59%, respectively. After thermal treatment at 200 °C for 2 h on the active layer,the PCE of the PSC based on J63 still keeps 92% of the original value, which verifies that the cross-linking of the polymer can improve the thermal stability of PSCs. Morphological studies show that the active layer based on J63 displays strong lamellar packing with RMS 1.26, and the active layer based on J64 shows little phase separation with RMS 0.65. The RMS of the active layer based on J62 is 0.900, and the size of phase separation is between that of J63 and J64, which indicates the excessive high lamellar packing or low phase separation is harmful to the performance of PSCs. These results indicate that the side-chain engineering is an effective way to adjust the aggregation of polymers and the morphology of blend films, which are key factors to influence the performance of PSCs

A Synthetic Route for Crystals of Woven Structures, Uniform Nanocrystals, and Thin Films of Imine Covalent Organic Frameworks

Developing synthetic methodology to crystallize extended covalent structures has been an important pursuit of reticular chemistry. Here, we report a homogeneous synthetic route for imine covalent organic frameworks (COFs) where crystallites emerge from clear solutions without forming amorphous polyimine precipitates. The key feature of this route is the utilization of <i>tert</i>-butyloxycarbonyl group protected amine building blocks, which are deprotected <i>in situ</i> and gradually nucleate the crystalline framework. We demonstrate the utility of this approach by crystallizing a woven covalent organic framework (COF-112), in which covalent organic threads are interlaced to form a three-dimensional woven framework. The homogeneous imine COF synthesis also enabled the control of nucleation and crystal growth leading to uniform nanocrystals, through microwave-assisted reactions, and facile preparation of oriented thin films

Mesoscopic Constructs of Ordered and Oriented Metal–Organic Frameworks on Plasmonic Silver Nanocrystals

We enclose octahedral silver nanocrystals (Ag NCs) in metal–organic frameworks (MOFs) to make mesoscopic constructs <i>O</i>_<i>h</i>-nano-Ag⊂MOF in which the interface between the Ag and the MOF is pristine and the MOF is ordered (crystalline) and oriented on the Ag NCs. This is achieved by atomic layer deposition of aluminum oxide on Ag NCs and addition of a tetra-topic porphyrin-based linker, 4,4′,4″,4‴-(porphyrin-5,10,15,20-tetra­yl)­tetra­benzoic acid (H₄­TCPP), to react with alumina and make MOF [Al₂(OH)₂­TCPP] enclosures around Ag NCs. Alumina thickness is precisely controlled from 0.1 to 3 nm, thus allowing control of the MOF thickness from 10 to 50 nm. Electron microscopy and grazing angle X-ray diffraction confirm the order and orientation of the MOF by virtue of the porphyrin units being perpendicular to the planes of the Ag. We use surface-enhanced Raman spectroscopy to directly track the metalation process on the porphyrin and map the distribution of the metalated and unmetalated linkers on a single-nanoparticle level

Reconfigurable LC Elastomers: Using a Thermally Programmable Monodomain To Access Two-Way Free-Standing Multiple Shape Memory Polymers

This work details a novel polyurethane liquid crystal elastomer (PULCE) with exchangeable carbamate functional groups that enable programming of a uniformly aligned monodomain sample through the application of external stress and simultaneous activation of dynamic bond exchange of the carbamate. PULCEs were synthesized using a thiol-Michael addition reaction, and the reversion of the carbamate group was observed by real-time FT-IR and mechanical analysis. Two independent phase transitions (isotropic–nematic and nematic–smectic) were employed to actuate two-way autonomous strains and multiple shape memory effects in a single system. In addition, thermally activated bond exchange engineered into the network transformed the permanent configuration of the material into various complex shapes. The programmed network topology and bond exchange conditions controlled the two-way autonomous shape changes. Coupling the shape memory effect of the polymer network with the plasticity induced by the thermally activated dynamic covalent chemistry in shape changing and shape memory materials will expand their applications and capabilities in emerging multifunctional devices