Oligoethyleneoxide spacer groups in polymerizable surfactants

Cationic and zwitterionic polymerizable surfactants bearing tri- and tetraethyleneglycol spacer groups between the polymerizable moiety and the surfactant structure were prepared and polymerized. Monomers and polymers were investigated with respect to their aggregation behavior in aqueous systems and compared to analogous monomers and polymers lacking spacer groups. In the case of the monomeric surfactants, the spacer groups depress both the Kraffttemperature and the critical micelle concentration. the area occupied per molecule at the air-water interface is substantially enlarged by the spacers, whereas the depression of surface tension is nearly constant. Although the monomers with and without spacers are true surfactants, all the polymers are water-insoluble, but form monomolecular layers at the air-water interface. In analogy to the monomer behavior, the incorporation of the spacer groups increases the area occupied per repeat unit at the air-water interface substantially, but hardly affects the surface activity.     

Designer multi-functional comb-polymers for surface engineering of quantum dots on the nanoscale

Synthesis, characterization and cell-biomarker applications for a novel series of comb-copolymers featuring hydrophobic amide side groups, carboxylates and other functionalities such as polymerizable side chains and PEG oligomers are reported. When used as polymer ligand shell for trioctylphosphine oxide (TOPO) coated quantum dots (QDs) these copolymers effectively solubilise CdSe/ZnS QDs in water. A systematic study was carried out to find the relation between the molecular structure of the copolymers, their ability to coat the QDs, and to suspend the nanocrystals in water. To demonstrate potential applications, highly luminescent QD/polymer assemblies were internalized into living and fixed cells.     

Biomimetic interactions of proteins with functionalized cadmium sulfide quantum dots

Interactions between various modified semiconductor nanocrystal, cadmium sulfide quantum dots (CdS QDs) and bovine serum albumin (BSA) and lysozyme (LZY) were investigated. CdS QDs capped with mercaptoethanol (MPA), l-cysteine (Lcys) and glutathione (GSH) were synthesized in aqueous solution and characterized by UV-vis and fluorescence spectrum. Circular dichroism (CD) and fluorescence spectrum were used to detect the interactions between as-prepared CdS QDs and protein molecules. The interaction parameters, including binding constant (K_b), binding site number (n) and quench constant (K_q), were determined by fluorescence spectrum. The changes of secondary structures of the proteins were detected by CD. The results imply that CdS QDs modified by different agents have dramatically different binding strength with protein molecules. The results obtained here analyze the biosafety of CdS QDs in terms of the biological behavior of biomolecules and could serve as basis for the application of CdS QDs to bioscience.     

Functionalized monomers based on N-(4-hydroxy phenyl)maleimide

N-(4-Hydroxy phenyl)maleimide (HPMI) is functionalized with acryloyl, methacryloyl, allyl, propargyl and cyanate groups and the structures of the materials are characterized by FTIR, ¹H NMR and ¹³C NMR. Thermal curing behaviours of the monomers and thermal stabilities of the polymers are studied using thermal analysis. Introduction of polymerizable groups shifts the curing exotherm to low temperatures, and the curing behaviour is dictated by the polymerizable substituent present in the aromatic ring. Polymer from acryloyl-functionalized monomer shows the highest thermal stability (402 °C), whereas the highest char value (49 % at 700 °C) is noted for the polymer obtained from propargyl-functionalized monomer. Polymers derived from functionalization of HPMI with acryloyl and methacryloyl showed better thermal stabilities. Thermosets formed by the thermal polymerization of HPMI functionalized with propargyl and cyanate groups showed higher char values at 700 °C in nitrogen atmosphere.     

Synthetic routes to block copolymerization by changing mechanism from cationic polymerization to free radical polymerisation

Polymers containing thermolabile groups were synthesized by various cationic polymerization initiation mechanisms, namely; oxo–carbenium, promoted cationic and activated monomer polymerization. These polymers used in a subsequent blocking step in which azo groups were decomposed and converted into initiating centres from which blocks were grown by means of free radical polymerization. This procedure was applied to specific systems in which cationic polymerizable monomers are tetrahydrofuran (THF), cyclohexene oxide (CHO) and epichlorohydrin (ECH), respectively, and the free radical polymerizable monomer is styrene (St).     

Characterization of molecularly imprinted polymers employing crosslinkers with nonsymmetric polymerizable groups

Crosslinking monomers have been developed with a combination of methacrylamide and methacrylate or vinyl ketone polymerizable groups that provide molecularly imprinted polymers (MIPs) with improved binding and selectivity. The differential reactivity rates of the polymerizable groups prompted an investigation into the time‐dependent behavior of the crosslinkers, which suggests a new mechanism for MIP formation. The mechanism involves the formation of long sections of linear poly(vinyl ketone) with pendant methacrylamide groups that form a highly crosslinked network in a subsequent step. This has implications for the sequence morphology of polymers, affecting the structure and improving the binding properties of MIPs. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3668–3675, 2004     

Microstructure and lateral diffusion in monolayers of polymerizable amphiphiles

Lipid analogue amphiphilic molecules containing polymerizable units were investigated in monolayers at the air/water interface by using film balance measurements, fluorescence microscopy, and photobleaching techniques. The polymerizable groups (diene-, diyne-, and methacrylate units) were introduced into the hydrophobic alkyl chains or into the polar head of the amphiphilic molecules.In the case of the diene- and diyne-containing compounds the polymerizable units are incorporated into the hydrophobic alkyl chains, enabling them to form a two-dimensional network. Due to the free chain flexibility of the monomers the lateral mobility was comparable to that of saturated lipid analogues and decreases upon polymerization proportionally to the dose of UV irradiation. In addition, fluid/solid phase transitions of compounds with polymerizable groups in the hydrophobic part tend to vanish during the formation of the polymers. However, the direct observation of the growth of polymeric crystalline domains can be followed by using diacetylene lipid analogues.In the case of the methacrylate derivatives the polymerizable unit was coupled to the polar part via a flexible spacer. For these systems the characteristics of the monomeric phase transition are retained after polymerization. However, it shows a significant, strong decrease of the in-plane mobility already in the fluid-expanded phase of the polymer. The quantitative measurements of the lateral diffusion in the monolayers can be correlated with fluorescence microscopic images of their structure.     

Core Cross-Linked Polymerized Micelles and Dendronized Nanoparticles

Polymerization of 11-acryloylaminoundecanoic acid and its copolymerization with diacrylic monomers were performed under different conditions in micellar (Na-salt in water) and non-micellar states. The effect of conditions of the syntheses on molecular mass of the polymers and hydrodynamic characteristics of their macromolecules was studied. Ionic complexes of core-cross-linked polymerized micelles with different dendrons bearing polymerizable peripheral groups were obtained and their trial polymerizations were performed.     

FUNCTIONAL POLYMERS 65. SYNTHESIS AND BRIEF CHARACTERIZATION OF SURFACE ACTIVE 2(2-HYDROXYPHENYL)2H-BENZO-TRIAZOLE ULTRAVIOLET STABILIZERS

A number of 2(2-hydroxyphenyl)2H-benzotriazoles substituted in the 5-position with reactive hydroxyl and carboxyl groups have been synthesized. They include compounds with a tert butyl substitution in the 3-position or without substitution. The latter compounds were subjected to a reaction with N-hydroxy-methyl-(meth)acrylamide to form acrylic polymerizable 3(meth)acrylamidomethyl-2(2-hydroxyphenyl)2H-benzotriaz-oles. Hydroxyl reactive compounds were allowed to react with long chain acids, compounds with carboxyl groups with long chain hydrocarbon, fluorocarbon or silicon oligomer alcohols. The polymerizable 2(2-hydroxyphenyl)2H-benzotriazoles were then copolymerized with methyl methacrylate. Films made from such polymers showed by contact angle measurements, substantial migration of the fluorocarbon or silicon component to the surface of the film.     

Synthesis of a Diverse Library of N,N-Dimethylamino Containing Monomers Appropriate as Lipid Head Groups

We report on the synthesis of a diverse library of N,N-dimethylamino containing monomers. Subjecting these monomers to Chabrier reaction conditions would yield lipids with polymerizable head groups. This library of lipid head groups is equipped with arms of various lengths containing reduction-oxidation polymerizable groups at the terminus.     

Polymerization of asymmetric polyfunctional monomers. III. Ionic polymerization of acrylic and methacrylic esters of 2-allylphenol

The polymerization of acrylic and methacrylic esters of 2-allyphenol with different anionic, cationic and coordination catalysts was studied. The polymerization occurs exclusively or predominantly through (meth)acrylic C?C double bonds in all the studied cases. With anionic catalysts the allylic groups are not polymerizable and the polymers have linear structure. Polymerization with catalysts based on dialkylaluminum chloride (alone or associated with some metal salts) yields soluble or partially crosslinked polymers, depending on the reaction conditions. The crosslinking is due to the participation of allylic groups in the polymerization reactions. Copolymers of acrylic and methacrylic esters of 2-allylphenol with styrene, acrylonitrile, methyl methacrylate, N-vinylcarbazole and 1,3-pentadiene were synthesized by copolymerization in the presence of anionic catalysts and of systems based on dialkylaluminum chloride.     

Langmuir-Blodgett thin films of quantum dots: synthesis, surface modification, and fluorescence resonance energy transfer (FRET) studies

We describe herein studies on as-prepared hydrophobic ZnS-CdSe quantum dots (QDs) at the air-water interface. Surface pressure-area (pi-A) isotherms have been used to study the monolayer behavior. Uniform, lamellar multilayer thin films of QDs were deposited by the Langmuir-Blodgett (LB) technique. The role of two different surfactant systems commonly employed in the synthesis of these QDs (trioctylphosphine oxide-octadecylamine (TOPO-ODA) system and trioctylphosphine oxide-tetradecylphosphonic acid (TOPO-TDPA) system) on the monolayer behavior and the quality of thin films produced has been investigated. The thin films were characterized by quartz crystal microgravimetry (QCM), contact angle measurements, fluorescence spectroscopy, and transmission electron microscopy (TEM). These QD films were further modified by an amphiphilic polymer, poly(maleic anhydride-alt-1-tetradecene) (PMA). The hydrophobic interaction between the polymers and the surfactants attached to the QDs drove the self-assembly process. The carboxylic acid functional groups in the polymer were also used to immobilize avidin. We have demonstrated a proof of concept for the biosensing strategy wherein the avidin-coated QD films attracted biotinylated gold nanoparticles, resulting in fluorescence resonance energy transfer (FRET) quenching of the thin films.     

NEW BLUE CROSSLINKABLE POLYMERS FOR ORGANIC LIGHT EMITTING DEVICES

Here, we report on new blue electroluminescence (EL) crosslinkable polymers containing fluorene/phenylene alternating repeating units. Additionally, they contain polymerizable oxetane groups attached through flexible hexyloxy chains to phenylene units of the polymer backbone. The copolymers were synthesized via Pd-catalyzed Suzuki coupling reactions. The copolymers obtained were found to be soluble and easily processable from common organic solvents such as chloroform or toluene and have been characterized by ¹H and ¹³C NMR spectroscopy, FT-IR spectroscopy and elemental analysis. The degree of polymerization has been determined by gel permeation chromatography (GPC). The thermal properties of the copolymers have been characterized by differential scanning calorimetry (DSC). The optical properties of the polymers were investigated in solution by UV/VIS spectroscopy. The polymers were photo-crosslinked in spin-coated thin films to yield insoluble networks.     

New Polymer Structures

A number of new polymers have been studied. They include polymers obtained by chain reaction polymerization of olefins and epoxides with functional groups where the polymerizable group was separated from the functional group by an inert spacer group, the preparation of head-to-head polymers, and the preparation of optically active polymers based on the macromolecular asymmetry.     

Synthesis and structure of polymerizable titanium complexes: elaboration of new mesoporous organometallic materials

Inertial confinement fusion (ICF) experiments generate a demand of specific organometallic materials, especially titanium-doped porous polymers obtained from specific Ti-containing monomers. Two new polymerizable titanium(IV) complexes were synthesized. Their free radical co-polymerization affords several titanium-containing polymers, which were dried under supercritical conditions to afford organic aerogels. The chemical compositions of these materials were investigated by NMR, IR, and elemental analysis while their structure was characterized by MEB-EDS and by N₂ adsorption/desorption isotherm measurements.     

Guest-responsive covalent frameworks by the cross-linking of liquid-crystalline salts: tuning of lattice flexibility by the design of polymerizable units

Cross-linked polymers prepared by the in-situ polymerization of liquid-crystalline salts were found to work as solid-state hosts with a flexible framework. As a component of such hosts, four kinds of polymerizable amphiphilic carboxylic acids bearing alkyl chains with acryloyloxy (A), dienyl (D), and/or nonreactive (N) chain ends (monomeric carboxylic acids; M(AAA), M(ANA), M(DDD), and M(DND)) were used. The carboxylic acids were mixed with an equimolar amount of a template unit, (1R,2S)-norephedrine (guest amine; G(RS)), to form the corresponding salts. Every salt exhibited a rectangular columnar LC phase at room temperature, which was successfully polymerized by (60)Co γ-ray-induced polymerization without serious structural disordering to afford the salt of cross-linked carboxylic acid (polymeric carboxylic acid; P(AAA), P(ANA), P(DDD), and P(DND)) with G(RS) . Owing to the noncovalency of the interactions between the polymer framework P and the template G(RS), the cross-linked polymers could reversibly release and capture a meaningful amount of G(RS). In response to the desorption and adsorption of G(RS), the cross-linked polymers dramatically switched their nanoscale structural order. A systematic comparison of the polymers revealed that the choice of polymerizable groups has a significant influence on the properties of the resultant polymer frameworks as solid-state hosts. Among these polymers, P(DDD) was found to be an excellent solid-state host, in terms of guest-releasing/capturing ability, guest-recognition ability, durability to repetitive usage, and unique structural switching mode.     

Thermodynamic and conformational investigation of the influence of CdTe QDs size on the toxic interaction with BSA

Water-soluble fluorescent colloidal quantum dots (QDs) have been widely used in some biological and biomedical fields, so the interaction of QDs with biomolecules recently attracts increasing attention. In this study, the fluorescence (FL) quenching method, circular dichroism (CD) technique, attenuated total reflection-Fourier transform infrared (ATR-FTIR) and UV-vis absorption spectra were used to investigate systematically the influence of CdTe QDs size on the toxic interaction with bovine serum albumin (BSA). Three size CdTe QDs with maximum emission of 543 nm (green-emitting QDs, GQDs), 579 nm (yellow-emitting QDs, YQDs) and 647 nm (red-emitting QDs, RQDs) were tested. The Stern-Volmer quenching constant (K_sv) at different temperatures, corresponding thermodynamic parameters (ΔH, ΔG and ΔS), and information of the structural features of BSA were gained. The FL results indicated that QDs can effectively quench the FL of BSA in a size-dependent manner, electrostatic interactions play a major role in the binding reaction, and the nature of quenching is static, resulting in forming QDs-BSA complexes. The CD and ATR-FTIR spectra showed that the secondary structure of BSA was changed by QDs, indicating the toxic on protein.     

Functionalization of polymers prepared by ATRP using radical addition reactions

Low molecular weight linear poly(methyl acrylate), star and hyperbranched polymers were synthesized using atom transfer radical polymerization (ATRP) and end‐functionalized using radical addition reactions. By adding allyltri‐n‐butylstannane at the end of the polymerization of poly(methyl acrylate), the polymer was terminated by allyl groups. When at high conversions of the acrylate monomer, allyl alcohol or 1,2‐epoxy‐5‐hexene, monomers which are not polymerizable by ATRP, were added, alcohol and epoxy functionalities respectively were incorporated at the polymer chain end. Functionalization by radical addition reactions was demonstrated to be applicable to multi‐functional polymers such as hyperbranched and star polymers.     

Radical graft polymerization onto composite particles of polydimethylsiloxane and polybutadiene

Submicron-size composite polymer particles consisting of polydimethylsiloxane/core and polybutadiene/shell were synthesized by seeded emulsion polymerization. The morphologies of composite particles were affected by polybutadiene ratio in the composite particles. Highly grafted polymer by poly(styrene-co-acrylonitrile) could be prepared by using the composite particles containing polybutadiene with polymerizable group. The morphologies of the grafted polymer were influenced by the morphologies of composite particles and the kinds of grafting initiators. It was found that surface gloss and lubricity of the graft polymers were influenced by morphologies of composite particles.     

Core/shell quantum dots in ferroelectric liquid crystals matrix: effect of spontaneous polarisation coupling with dopant

In order to fabricate efficient and superior performance liquid crystal (LC) devices, the physical parameters of the LC mesogens can be duly altered by incorporating non-mesogenic materials like quantum dots (QDs), graphene and polymers. In the present work, the effect of adding core/shell QDs in two ferroelectric liquid crystals (FLCs), along with the change in their physical properties, has been investigated. A small concentration of QDs is dispersed into the two FLCs and temperature variations of vital parameters like spontaneous polarisation (P_s), rotational viscosity, response time, relative permittivity and relaxation strength have been measured for both the FLC materials. The contrast ratio, UV–near visible absorbance as well as photoluminescence (PL) of both the mesogens have also been determined and compared. A faster electro-optical response and the induced phenomenon of PL with a temperature-dependent low-frequency relaxation mode have been observed in Felix 17/100 after the addition of QDs. The present study also provides valuable information about the interaction between QDs and the two FLC systems depending upon polarisation–field (P–E) coupling. The same dopant can interact with FLCs in dissimilar fashion if the intrinsic properties of both the FLCs are different thereby producing different modifications in their respective physical parameters.