Synthesis and properties of room temperature curable trimethoxysilane‐terminated polyurethane and their dispersions

The purpose of this research is to study the synthesis and characterization of stable aqueous dispersions of externally chain extended polyurethane/urea compositions terminated by hydrolyzable or hydrolyzed trialkoxysilane groups incorporated through secondary amino groups. These dispersions with excellent storage stability are substantially free from organic solvents which cure to water and solvent resistant, tough, scratch resistant, preferably light stable (non‐yellowing) silylated polyurethane (SPU) films. The films were characterized by FT‐IR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile strength and water contact angle measurements, nanoindentation, gel content, water and xylene swellability tests. The properties of the films were discussed and correlated in detail by changing length of soft segment, diisocyanates, NCO/OH ratio and chain extender, ethylenediamine (EDA). From the results, it was found that the particle size and viscosity are lower whereas the gel content and thermal stability are higher for SPUs. Modulus, hardness and tensile properties of SPU films are superior compared to EDA‐PU film. Higher water contact angle and residual weight percentage of SPU films confirm silylation of PU by [3‐(phenylamino)propyl]trimethoxysilane (PAPTMS). Increase in NCO/OH ratios consumes more quantity of PAPTMS which makes PU with superior mechanical properties. Higher PAPTMS content in SPU results in effective crosslinking of the functional silanol groups formed by hydrolysis reaction of trimethoxysilane groups. Overall, SPUs synthesized at 1.4 NCO/OH ratio using Poly‐(oxytetramethylene)glycol (PTMG)‐2000 and isophorone diisocyanate (or) toluene‐2,4‐diisocyanate have excellent properties compared to SPUs prepared using PTMG‐1000 and at 1.2 and 1.6 NCO/OH ratios. SPUs prepared at 1.6 NCO/OH ratio are brittle due to higher crosslinking density. In addition, the crosslinking density of the films can be modified through silane end‐group modification to produce SPUs with a wide range of physical properties. Copyright © 2007 John Wiley & Sons, Ltd.     

具有明确硬段结构的水性聚氨酯脲的研究

通过逐步反应由4,4′-二苯基甲烷二异氰酸酯、2,2-二羟甲基丙酸和1,4-丁二醇,合成了结构明确的硬段模型化合物.通过13C NMR对其序列结构进行了表征,并通过FTIR、DSC和WAXD对其形态结构进行了研究.进一步制备了具有这类规整结构硬段的水性聚氨酯脲,初步考察了水分散液及其成膜后的性能.实验结果表明,这类聚氨酯脲水分散液的粒径小于110nm,在室温下贮存期大于一年,成膜后具有优异的耐水性能以及表面疏水性能.     

PREPARATION OF WATERBORNE ULTRAFINE PARTICLES OF EPOXY RESIN BY PHASE INVERSION TECHNIQUE

Werborne ultrafine particles of epoxy resin were prepared by phase inversion tech-nique. The results of SEM revealed that the particles diameter was in the range of 50to 100 nm and the effects on amount of water required at phase inversion point were alsodisc?d.     

Random photografting of polymers to nanoparticles for well-dispersed nanocomposites

A simple method to achieve dispersion of nanoparticles (NPs) within polymer matrices by solution-state photografting of benzophenone (BP)-containing random copolymers is presented. A benzyl ether ligand that stabilizes NPs in solution while possessing selectivity toward hydrogen abstraction and subsequent coupling with BP was designed. This method for introducing grafts by ultraviolet (UV) light exposure affords control over the dispersion state in the resulting polymer films, as revealed by transmission electron microscopy and UV–visible spectroscopy. The evolution of the hydrodynamic sizes of particles as a function of UV dose suggests that the polymers “wrap” particles by forming multiple attachment points per chain because of the relatively rapid kinetics for the formation of subsequent attachments following the first grafting event for a given chain. In addition, the presence of unreacted BP groups allows for photolithographic patterning of well-dispersed nanocomposite films. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 152–158     

Random copolymers at a selective interface: Many chains with excluded volume interactions

We investigate numerically, using the bond-fluctuation model, the adsorption of many random AB-copolymers with excluded volume interactions at the interface between two solvents. We find two regimes, controlled by the total number of polymers. In the first (dilute) regime, the copolymers near the interface extend parallel to it, while in the second regime they extend perpendicular to it. The density at the interface and the density in the bulk depend differently on the total number of copolymers: In the first regime the density at the interface increases more rapidly than in the bulk, whereas the opposite is true in the second regime. Received 4 March 1998 and Received in final form 22 September 1998     

Colonic drug delivery using amylose films: the role of aqueous ethylcellulose dispersions in controlling drug release

Amylose, a plant polysaccharide from starch, can be combined with ethylcellulose to produce a film coating capable of effecting colon specific drug release from a dosage form through bacterial fermentation of the amylose component. Ethylcellulose is present in the system as a structuring agent in the form of the aqueous dispersion Surelease^® grade EA-7100. There are, however, two other grades of Surelease^® (E-7-7050 and E-7-19010), which vary slightly in terms of their composition. The aim of the study was to establish whether these grades differ in their drug release profiles, when used as a film coat, either as one-component coatings, or in combination with amylose. The dissolution profiles of Surelease^® coated pellets were investigated and it was found that there was no difference between the grades when used as coating materials on their own. However, when used in combination with amylose, it was found that grade EA-7100 showed retardation of drug release in simulated upper gastro-intestinal (GI) conditions, whereas grades E-7-7050 and E-7-19010 did not limit the release to the same extent. E-7-19010 showed very poor controlled release properties when combined with amylose. These differences could not be attributed to the minimum film forming temperature (MFT) of the coating formulation, which was found to be independent of the grade of Surelease^®. It was also confirmed that the film coated pellets prepared from amylose and EA-7100 showed good release in human faecal slurry, i.e. simulated colonic conditions. It was concluded that the grades of Surelease^®, when combined with amylose, are not interchangeable.     

Synthesis of water‐dispersible,fluorinated particles with grafting sulfonate chains by the core crosslinking of block copolymer micelles

Fluorinated polymer particles with grafting sulfonate chains, which showed high dispersion stability in aqueous media, were synthesized by the crosslinking of block copolymer micelles. A crosslinkable block copolymer, poly[(2,3,4,5,6‐pentafluorostyrene)‐co‐4‐(1‐methylsilacyclobutyl)styrene]‐b‐poly(neopentyl 4‐styrenesulfonate), composed of a statistical copolymer segment of 2,3,4,5,6‐pentafluorostyrene with 4‐(1‐methylsilacyclobutyl)styrene and a neopentyl 4‐styrenesulfonate segment, was prepared by the nitroxy‐mediated living radical polymerization of a 2,3,4,5,6‐pentafluorostyrene/4‐(1‐methylsilacyclobutyl)styrene mixture and neopentyl 4‐styrenesulfonate. The block copolymer formed micelles with a poly[(2,3,4,5,6‐pentafluorostyrene)‐co‐4‐(1‐methylsilacyclobutyl)styrene] core in acetonitrile, which were crosslinked via the ring‐opening reaction of silacyclobutyl groups in the core by a treatment with a platinum catalyst. The deprotection of sulfonate groups in the micelle corona by exposure to trimethylsilyl iodide and a treatment with aqueous HCl, followed by neutralization with aqueous NaOH, provided a polymer particle with polymer chains of sodium 4‐styrenesulfonate grafted on its surface. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1316–1323, 2007     

Preparation of porous biodegradable microspheres with direct melting dispersion method

Porous biodegradable microspheres can be prepared by using the direct melting dispersion method without any noxious organic solvents, in which the biodegradable polymer is directly melted and stirred to form the liquid–liquid dispersion followed by cooling in the continuous phase, such as ethylene glycol with the higher melting temperature than polymer. In the experiment, polyhydroxybutyrate (PHB) was adopted as the biodegradable polymer. As particulate porogen, magnetite powder was pre‐mixed into the melted polymer and removed by hydrochloric acid aqueous solution after preparation of the microspheres to make them porous. It was found that the inner surface area was significantly increased by removing magnetite powder. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis of polymeric core–shell particles using surface‐initiated living free‐radical polymerization

An easy and novel approach to the synthesis of functionalized nanostructured polymeric particles is reported. The surfactant‐free emulsion polymerization of methyl methacrylate in the presence of the crosslinking reagent 2‐ethyl‐2‐(hydroxy methyl)‐1,3‐propanediol trimethacrylate was used to in situ crosslink colloid micelles to produce stable, crosslinked polymeric particles (diameter size ～ 100–300 nm). A functionalized methacrylate monomer, 2‐methacryloxyethyl‐2′‐bromoisobutyrate, containing a dormant atom transfer radical polymerization (ATRP) living free‐radical initiator, which is termed an inimer (initiator/monomer), was added to the solution during the polymerization to functionalize the surface of the particles with ATRP initiator groups. The surface‐initiated ATRP of different monomers was then carried out to produce core–shell‐type polymeric nanostructures. This versatile technique can be easily employed for the design of a wide variety of polymeric shells surrounding a crosslinked core while keeping good control over the sizes of the nanostructures. The particles were characterized with scanning electron microscopy, transmission electron microscopy, optical microscopy, dynamic light scattering, and Raman spectroscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1575–1584, 2007     

Polyelectrolyte complex dispersions with a high colloidal stability controlled by the polyion structure and titrant addition rate

Three ionic/nonionic random copolymers of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS) with either t-butyl acrylamide (TBA) or methyl methacrylate (MM), were used in the preparation of some polyelectrolyte complex dispersions (PCD) with two strong polycations of integral type, poly(diallyldimethylammonium chloride) (PDADMAC), and an ionene type polycation, containing 95 mol% N,N-dimethyl-2-hydroxypropyleneammonium chloride repeat units (PCA₅). The novelty of the paper is that PCDs with a high colloidal stability, both before and after the complex stoichiometry, were obtained even with hydrophilic/hydrophobic polyanions, with a high titrant addition rate (TAR), a less explored parameter, which allows a fine control of PCDs aggregation level, in salt-free aqueous solutions. The characteristics of PCDs were also correlated with the polyanion average charge density and the structure of the nonionic comonomer, at a constant TAR, the polyanion with the lowest charge density leading to the highest turbidities and the lowest colloidal stabilities. A mechanism of the PCDs colloidal stabilization as a function of TAR was suggested in the paper.