Summary: The polylactide‐based nano‐composites were prepared via melt extrusion method using different types of intercalants and nano‐fillers having different surface charge density. In order to understand the direct polymer melt intercalation into the nano‐galleries, the interdigitated layer structure of the organically modified layered filler (OMLF), where the intercalants are oriented with some inclination to the host layer in the interlayer space, was proposed. After polymer melt intercalation, the smaller initial interlayer opening led to the larger interlayer expansion, suggesting the large amount of the intercalation of the polymer chains. Consequently, the nano‐composite exhibited finer dispersion of the nano‐fillers when compared with the nano‐composites prepared from OMLFs with larger initial interlayer opening.
Illustration of a model of interlayer structure of the qC14(OH) in gallery space of HTO. 相似文献
Photolabile polymer brushes with tailored length containing a photoremovable protecting group (NVOC) are prepared via the SI‐ATRP method. Upon light irradiation, the NVOC group is removed to generate controlled densities of free amine groups (PAMA) randomly distributed along the brush. The presence of the ionizable groups induces a photo‐triggered swelling response. The swelling degree can be tuned by the irradiation dose. A dual (light and pH), tunable response is demonstrated.
1‐Vinyl‐2‐(hydroxymethyl)imidazole ( 2 ) is synthesized by a procedure described in the literature. Corresponding copolymers with upper critical solution temperature (UCST)‐type transitions in water and high‐glass transition temperatures (Tg) are prepared by free radical copolymerization with N‐vinylimidazole ( 1 ). Depending on the copolymer composition, the cloud point can be varied between 19 and 41 °C. As the copolymer composition is identical with the monomer feed ratio, the cloud point can be easily tuned in the desired range. Furthermore, a distinctive pH‐dependence and salt effect can be observed.
Grafted conjugated polyelectrolytes were synthesized for the first time and characterized. The polymers demonstrated properties of a convenient and efficient protocol for creating Hg2+ sensors. The unique character of the new material comes from an anionic counterion nature with no external cofactors, and imparts high selectivity and fast detection for mercury ion in a fluorescence probe. The concept may be potentially applied to create new sensors for monitoring other ions.
Readily water‐soluble PEGylated amphiphiles containing bis‐thiourea‐based molecular recognition units at the interface of hydrophobic and hydrophilic blocks are developed. Self‐assembly of these amphiphiles is found to be dependent on the exact chemical composition of the hydrophobic component. Elongated, spherical, and disk‐like micelles are formed with the change in hydrophobic group from stearyl (2A), oleyl (2B), and dodecanol (2C), respectively. The length of the rod‐like elongated micelles formed by 2A could be tuned by thermal treatment as well. Synthesis and detailed structural characterization of these amphiphiles by TEM, DSC, synchrotron SAXS techniques are reported. Organic solvent‐free direct aqueous encapsulation of doxorubicin, an anticancer drug into these nanostructures is demonstrated.
This review article describes the preparation of polymer brushes by nitroxide‐mediated radical polymerization using either the ‘grafting to’ or the ‘grafting from’ approach. The use of TEMPO as a classical initiator is intensively described. More sophisticated nitroxides are also included in the discussion. Brush formation on flat surfaces such as wafers and also on particles is reported. Finally, some applications of polymer brushes are presented.
The thermally and flow induced crystallization behavior of polymer melts has been investigated by using penalty finite element‐finite difference simulation with a decoupled solving algorithm. The coexistence model of spherulite and shish‐kebab is proposed to describe the evolution of crystallization kinetics process. The Schneider equation and Eder equation are adopted to discriminate the relative roles of the thermal and the flow effect on the crystallization behavior. The proposed mathematical model and numerical method have been successfully applied to the investigation of crystallization behavior in the hollow‐profile extrusion process. Both the evolution of crystalline size within the extrusion die and the effects of processing conditions on the crystallization kinetics process are discussed.
Summary: An initiator for nitroxide mediated ‘living’ free radical polymerization was prepared with a fluorescent tag attached to the initiating alkyl radical terminus. This was used to synthesize amphiphilic poly(acrylic acid)‐block‐polystyrene diblock copolymers, which self assembled in a tetrahydrofuran/buffer solution to form structures that are visible by fluorescence.
The nucleophilic living ring‐opening polymerization of N‐substituted glycine N‐carboxyanhydrides using solid‐phase synthesis resins is reported. By variation of experimental parameters, products with near Poisson distributions are obtained. As opposed to reversible deactivation radical polymerization, the living polymerization is demonstrated to be viable to high monomer conversion and through multiple monomer addition steps. Successful preparation of a multiblock copolypeptoid is proof for a highly living and robust character of the solid‐phase peptoid polymerization.
Summary: A novel experimental set‐up has been devised to measure simultaneously, in real time, the conversion and shrinkage of multi‐acrylates during photopolymerization. The data show that the current practice of assigning the excess volume entirely as excess free volume is inappropriate as this leads to an increasing fractional free volume with conversion. We propose to partition the excess volume into free and occupied volume components. The new model produces satisfactory results.
Experimental set‐up for the simultaneous collection of shrinkage and conversion data. 相似文献
Summary: The fracture properties of polymers are one of the key parameters that define their service life and limit their applications. One of the most interesting and important questions is how the molecular architecture and the structure of polymers at nanolength scales influence their fracture properties. X‐ray scattering is a powerful means of probing bulk structures at the nanometre scale. It can therefore provide a wealth of information relating to such structure‐property relationships. In the present study, synchrotron radiation microfocus small‐angle X‐ray scattering is used to investigate the damage area ahead and around the crack tip in polyamide 6 (PA6). The results reveal that the damage area propagates far beyond the visible crack, and inside the damaged zone platelet‐shaped cracks/voids are formed.
Water‐soluble single‐ and multi‐walled carbon nanotubes (CNTs) were prepared by grafting polyacrylamide chains from the graphitic surface via ceric ion‐induced redox radical polymerization. The reducing functionalities were covalently attached to the tubes by peroxide‐assisted radical reaction. The results showed that polymer chains were grafted onto CNTs by the redox process. The redox radical polymerization initiated by carbon nanotube‐bearing functionalities not only provides a powerful strategy for modifying the carbon nanostructures but also gives us the knowledge of their sidewall chemistry.
Summary: The nanostructuring of ORMOCER® to form inverse opals is described. For this purpose a polymer opal is used as a template and infiltrated with liquid ORMOCER®. After photopolymerization of the resin the host opal is dissolved in tetrahydrofuran and an ORMOCER® inverse opal is obtained. It shows excellent periodicity (by SEM) and optical properties to reveal a high degree of face centered cubic order. This replication process leads to a nanostructured photonic crystal with the outstanding mechanical properties of ORMOCER® and high temperature stability up to 350 °C.
ORMOCER® inverse opal annealed at 200 °C for 10 h. 相似文献
But‐3‐en‐1‐ol has been pre‐protected by triisobutylaluminium and terpolymerized with ethylene and norbornene by rac‐[Et(Ind)2]ZrCl2/MAO catalysts. The strong polarity of diisobutyl(but‐3‐en‐1‐oxy)aluminum causes a slight reduction in the catalyst activity and yields a small fraction of crystallinity. The but‐3‐en‐1‐ol content in the terpolymer is as high as 3.2% and can be readily adjusted by varying the reaction conditions. When the norbornene/ethylene ratio is over 10, the norbornene incorporation efficiency is not affected by the polar monomer and is close to that of the copolymerization. Similar to the ethylene/norbornene copolymers, the thermal properties of the obtained terpolymers are mainly determined by their norbornene contents.
In this work, a color‐oscillating system is first developed by combining the intrinsic peristaltic motion of a Landolt pH‐oscillator with the structure color of a well‐designed pH‐sensitive photonic crystal hydrogel. As a result, the pH oscillation reaction procedure could be distinctly monitored by the distinct change of structure color/optic signal. The oscillation rhythm of the pH well coincides with that of the stopband/structure color. The oscillation detail of each cycle can also be clearly monitored by color change. This work would be of great significance for the promising applications of real‐time monitoring of the microactuator by optical signal or structure color.
It is demonstrated that an optically transparent and electrically conductive polyethylene oxide (PEO) film is fabricated by the introduction of individualized single‐walled carbon nanotubes (SWNTs). The incorporated SWNTs in the PEO film sustain their intrinsic electronic and optical properties and, in addition, the intrinsic properties of the polymer matrix are retained. The individualized SWNTs with smaller diameter provide high transmittance as well as good electrical conductivity in PEO films.
Novel poly[(fluorene)‐co‐(2,8‐dioctyldibenzothiophene‐S,S‐dioxide‐3,7‐diyl)]s were synthesized. The octyl group on the 2,8‐dioctyldibenzothiophene‐S,S‐dioxide (DOSO) unit improved the solubility of the polymers and broadened the optical band gap from 2.95 to 3.20 eV as the content of DOSO unit increases. The electroluminescence (EL) spectra of polymers show CIE coordinates around (0.16, 0.07) independent of the ratio of DOSO units in the polymers, owing to the ICT and steric hindrance dual‐function. A high efficiency of 3.1 cd · A−1 (EQE = 3.9%) was obtained with the configuration of ITO/PEDOT:PSS/polymer/Ba/Al. The results indicate that PF‐3,7DOSOs could be a promising candidate for saturated blue‐emitting polymers with spectral stability and high efficiency.
A cationic water‐soluble polyfluorene (P2) containing a high density of tetraalkylammonium side chains in polymer backbone was synthesized and characterized. The polymer shows excellent water solubility up to 100 mg · mL−1 as well as high photoluminescence (PL) quantum yield of 44% in water. The relatively high cationic density and appropriate side chain length of the polymer are the key factors to achieve such high water solubility. The reduction potential of P2 is decreased as compared with its neutral polymer, reflecting the enhanced electron injection abilities. The standard NPB/Alq3 device using such a polymer as the electron injection layer shows nearly three‐fold enhancement in the electroluminescence (EL) efficiency.
