Influence of molecular weight on stepwise collapse of Langmuir monolayers of cyclolinear polyorganosiloxanes

 The series of hexacyclo-linear polyorganosiloxanes containing methyl and phenyl side groups, which differ by molecular weight and tacticity, were analyzed for the dependence of surface pressure on surface area per monomer unit. The effects of temperature and the nature of substrate were also investigated. All the polymers investigated are capable of forming Langmuir monolayers on the surfaces of liquid substrates. Being under compression, the monolayers of these polymers are able to form discrete multilayers. This property is closely related to the existence of thermodynamically stable mesophase in cyclolinear polyorganosiloxanes. It has been established that formation of the multilayers in these polymers is quite sensitive to the molecular weight of the polymer. This effect is explained by a change in the value of the shear module of the polymer with molecular weight. Received: 2 March 1998 Accepted: 20 July 1998     

侧链带长链烷酯基和胆甾酯基聚硅氧烷的合成及释药性能研究

报道了侧链带有长链烷酯基和胆甾酯基的聚硅氧烷的合成和相转变性质及由其组成的共混硅橡胶膜对避孕药物左旋十八甲基炔诺酮的释放性能,药物分子透过速率随温度的变化与共混膜中聚硅氧烷的结构和有序状态有关,由晶态转变为液晶态时,透过速率提高。     

Synthesis and Phase Behavior of Azo Dye Containing Liquid Crystalline Polyorganosiloxane

Abstract

A series of liquid crystalline polyorganosiloxanes containing both azo dye and cholesteryl groups were synthesized by reacting poly[3- chloroformylpropyl)methylsiloxane-co-dimethylsiloxane] with both cholesterol and 4-(4′-methoxyphenylazo)phenol. The yields were between 73 and 81%. Most of these new polyorganosiloxanes are colored solid products. Their chemical structures were confirmed by IR, ¹H NMR, and elemental analysis. Their phase behaviors were also investigated by using differential scanning calorimetry (DSC) and polarizing microscopy. The results show that all these polyorganosiloxanes exhibit liquid crystalline behavior at various temperatures and at any azo dye content. As a result of the orientation of both mesogenic azo dye and cholesteryl groups, smectic phases were formed beginning around 0°C, and cholesteric phases appeared above 60°C.     

Synthesis and Characterization of Functionalized Polyorganosiloxanes Containing Amino and Fluorocarbon Side Chains

A series of functional polyorganosiloxanes containing fluorocarbon side chain and amino groups had been synthesized by ring-opening polymerization. The raw materials used were Octamethyl cyclotetrasiloxane (D₄), dodecafluoroheptyl-propyl-trimethoxylsilane (502) and γ-aminopropyltriethoxylsilane (550), respectively. FTIR, ¹H-NMR, ¹³C-NMR, and ¹⁹F-NMR were used to characterize the copolymer structures. The surface properties of the functional polyorganosiloxanes emulsions were discussed. The results showed that the functional polyorganosiloxanes containing fluorocarbon and amino side chains had low surface tension and excellent water repellency.     

TEMPERATURE DEPENDENCE OF THE FLUORESCENCE SPECTRA OF LADDERLIKE POLYPHENYLSILSESQUIOXANE AND LADDERLIKE 1,4-PHENYLENE-BRIDGED POLYVINYLSILOXANE

Fluorescence spectra of ladderlike polyphenylsilsesquioxane (LPPS) and ladderlike 1,4-phenylene-bridgedpolyvinylsiloxane (LPPVS) have been measured as a function of temperature (4-55℃), in dilute tetrahydrofuran solution.The excimer (I_E) to monomer (I_M) intensity ratio (I_E/I_M) of LPPS dilute solution shows a double linear Arrhenius plot with abreak point ascribable to a transition temperature T_t This behavior has not been found for single chain polyorganosiloxanes.When InI_E of LPPS was plotted against I/T it also gave a double linear plot with one break point, which was found in singlechain polyorganosiloxanes. The different behaviors between LPPS and single chain polyorganosiloxanes may be mainlyattributed to the relatively rigid double-chain macromolecular backbone of LPPS. However, the In(I_E/I_M) of dilute LPPVSsolution versus I/T shows a simple linear variation with a positive slope which confirms our proposition. The differencebetween the fluorescence results of LPPS and those of LPPVS may possibly derive from their structure differences andcooperative motion in backbone chain bonds.     

Detection of environmental polyorganosiloxanes (silicones) by silicon-29 NMR spectroscopy

The utility of ²⁹Si NMR spectroscopy has been demonstrated on sediment-like materials in the quantitative and qualitative determination of polyorganosiloxanes (silicones) in selected environmental samples. This technique is highly selective for polydimethylsiloxanes (PDMS) and is non-destructive to the sample. Also, specific identification of polyorganosiloxanes in sediment is possible, in contrast to previous methods which provided only quantitative information while consuming the sample. The detection limit for a 9 h experiment is approximately 45 ppm.     

紫外光固化聚多氟烷氧丙基甲基硅氧烷的研究

本文报道几种紫外光敏有机硅单体:(γ-甲基丙烯酰氧)丙基甲基二甲氧基硅烷,1,3,5,7-四(γ-甲基丙烯酰氧丙基)四甲基环四硅氧烷和1,3-双(甲基丙烯酰氧甲基)-1,1,3,3-四甲基二硅氧烷的合成,以及它们与αH,αH,ωH-全氟烷氧丙基甲基环四硅氧烷的开环共聚反应,制备了一系列新型光敏聚多氟烷氧丙基甲基硅氧烷.并初步研究了在紫外光辐照下,这类光敏聚多氟烷氧丙基甲基硅氧烷的化学结构对固化速度的影响.     

Study the kinetics of thermolysis of textile materials modified by polyorganosiloxanes

Analysis of the parameters of thermal oxidative degradation of textile materials, modified commercial polyorganosiloxanes (DowCorning 3605, Silastic 9252/250 P) is performed. The influence of encapsulated adjuvants-refrigerant 23 (CHF₃) and ultrafine carbon-on the kinetic characteristics of thermolysis of cellulose fabrics is studied.     

Biodegradation of polyorganosiloxanes

Biodegradation of various polyorganosiloxanes (about 30 substances) under the influence of several biotype bacteria strain (16 types) were studied. A special procedure of biodegradation and analytical methods of evaluation the degree of degradation were applied. It was found that nearly all polysiloxanes tested are biodegradable but the degree of degradation depends on their composition and structure, as well as on the type of bacteria strain chosen.     

主链含环二硅氮烷硅橡胶水解稳定性的研究

<正> 一般说,硅氮键对水不稳定,因此聚硅氨烷尽管具有较好的耐热性,但是仍未得到应用。等指出,硅原子或氮原子上带有较大的空间位阻的基团后,如苯基等,可以提高硅氨烷的水解稳定性,取代基的电子效应对其水解稳定性也有影响。Fink发现     

Effect of aromatic protectors on the radiolysis of polyorganosiloxanes

The influence of phenyl and other aromatic groups on radiation crosslinking of polydimethylsiloxane and its mechanical blends and copolymers with polydiphenylsiloxane and polyphenylsilsesquioxane, radiation-induced gas evolution, and radical generation in these systems were considered. It was shown that radiation-chemical yields of crosslinking and gas evolution follow a simple exponential law over a wide concentration range of phenyl groups (at their content above 1 mol %). A similar dependence was observed for the radiation-chemical yield of hydrogen in ethylene copolymers with styrene. For the crosslinking processes, it was proved that the effect of phenyl groups is identical in the mechanical blends and copolymers of polyorganosiloxanes. The effect of retardation of radiation-chemical processes by phenyl groups was shown to be independent of whether one or two groups is linked to a silicon atom, it is their total amount that matters.     

Gasometric determination of alkyl radicals in polyalkylsiloxanes and silicofunctional organic silicon compounds

Summary We have worked out a gasometric method for determination of alkyl radicals (CH₃, C₂H₅) in polyorganosiloxanes and silicofunctional organic silicon compounds, based on their splitting as the corresponding hydrocarbons (CH₄, C₂H₆) by alkali. The accuracy of the method is 1–2%.     

硅氮化合物在改进聚硅氧烷热稳定性中的作用

本文研究了聚硅氧烷在硅氮化合物或二苯基二羟基硅烷、水以及它们同时存在下的热稳定性。硅氮化合物能使聚硅氧烷在350℃的热稳定性大大提高;而二苯基二羟基硅烷和水能促进硅氧烷主链的降介,但同时有硅氮化合物存在,这种促进作用将会消失。所以硅氮化合物能阻止由硅羟基和水引起的降介。同时也是获得耐350℃聚硅氧烷的简便方法。     

A new route for the preparation of liquid crystalline polyorganosiloxanes containing laterally linked mesogenic units on the main chains

A new route for the preparation of liquid crystalline polyorganosiloxanes containing laterally linked mesogenic units on the main chains (LLM-POS) is described. First, a novel polyorganosiloxane containing hydroquinone units on the main chains (HQ-POS) was synthesized by hydrosilylation polymerization. To avoid the oxygen silylation side reaction of phenolic groups, tetrahydropyranyl (THP) protective groups were used on the phenols taking part in the hydrosilylation reaction, the results indicating that THP groups are very stable and effective in hydrosilylation reactions. Then HQ-POS was further modified by a grafting reaction with 4- n -octyloxybenzoyl chloride, giving the desired LLM-POS, which has an increased molecular mass in comparison with similar polymers prepared by commonly used approaches. The titled LLM-POS was characterized by DSC, POM and XRD and shown to give smectic textures.     

A new route for the preparation of liquid crystalline polyorganosiloxanes containing laterally linked mesogenic units on the main chains

A new route for the preparation of liquid crystalline polyorganosiloxanes containing laterally linked mesogenic units on the main chains (LLM-POS) is described. First, a novel polyorganosiloxane containing hydroquinone units on the main chains (HQ-POS) was synthesized by hydrosilylation polymerization. To avoid the oxygen silylation side reaction of phenolic groups, tetrahydropyranyl (THP) protective groups were used on the phenols taking part in the hydrosilylation reaction, the results indicating that THP groups are very stable and effective in hydrosilylation reactions. Then HQ-POS was further modified by a grafting reaction with 4-n-octyloxybenzoyl chloride, giving the desired LLM-POS, which has an increased molecular mass in comparison with similar polymers prepared by commonly used approaches. The titled LLM-POS was characterized by DSC, POM and XRD and shown to give smectic textures.     

Preparation, characterization, and application of multistimuli-responsive microspheres with fluorescence-labeled magnetic cores and thermoresponsive shells

Novel functional microspheres with multistimuli-responsive properties have been prepared and characterized. The as-prepared microspheres respond to an external magnetic field, environmental temperature, and ultraviolet radiation. The in vitro drug-loading efficiency and drug-release behavior of these microspheres demonstrated that they could be used as drug carriers for drug controlled release. The results of in vivo distribution investigations of these microspheres showed that they exhibit a high magnetic-targeting effect, which holds promise for applications in various fields such as magnetic drug targeting and tissue labeling, among others.     

Hydroquinone oxidation catalyzed by pyridine–Cu(II) complexes attached to polyorganosiloxane. II. Elucidation of factors related to catalytic activity

The oxidation of hydroquinone catalyzed by pyridine-Cu(II) complexes attached to polyorganosiloxane was investigated in the mixed solvent of methanol/water (vol. ratio 2/1). The catalytic oxidation followed Michaelis-Menten-like kinetics. The large k₂ term related to a turnover number indicated that the present polymeric catalysts have a remarkable effect on the activation process. The methylene number between the side-chain acid amido and pyridyl groups of the polymeric ligand was shown to be closely related to the appearance of hydrophobic effects in both the substrate-binding and the activation processes as deduced from the Michaelis constant and the thermodynamic and activation parameters. The binding parameters for 4-methoxyphenol with pyridyl-functionalized polyorganosiloxanes supported that the flexible backbone is also effective in the oxidation of hydroquinone. The Cu(II) complexes with pyridyl-functionalized polyorganosiloxane would have the structures distorted from square planar formation, which would promote the reduction of Cu(II) to Cu(I), as concluded from ESR spectroscopy and electrochemical measurement. © 1994 John Wiley & Sons, Inc.     

温度及pH值敏感水凝胶的合成和应用

直接将丙烯酸单体与N-异丙基丙烯酸胺共聚交联合成了温度及pH值敏感的水凝胶。包埋于水凝胶中的药物的释放随温度升高和pH值增大而加快，药物的释放兼有温度和pH值敏感性，对pH值的响应更加显著。     

A novel rapid quantitative analysis of drug migration on tablets using laser induced breakdown spectroscopy

There have been few reports wherein drug migration from the interior to the surface of a tablet has been analyzed quantitatively until now. In this paper, we propose a novel, rapid, quantitative analysis of drug migration in tablets using laser induced breakdown spectroscopy (LIBS). To evaluate drug migration, model tablets containing nicardipine hydrochloride as active pharmaceutical ingredient (API) were prepared by a conventional wet granulation method. Since the color of this API is pale yellow and all excipients are white, we can observe the degree of drug migration by visual inspection in these model tablets. In order to prepare tablets with different degrees of drug migration, the temperature of the drying process after tableting was varied between 50 to 80 °C. Using these manifold tablets, visual inspection, Fourier transform (FT)-IR mapping and LIBS analysis were carried out to evaluate the drug migration in the tablets. While drug migration could be observed using all methods, only LIBS analysis could provide quantitative analysis wherein the average LIBS intensity was correlated with the degree of drug migration obtained from the drying temperature. Moreover, in this work, we compared the sample preparation, data analysis process and measurement time for visual inspection, FT-IR mapping and LIBS analysis. The results of the comparison between these methods demonstrated that LIBS analysis is the simplest and the fastest method for migration monitoring. From the results obtained, we conclude that LIBS analysis is one of most useful process analytical technology (PAT) tools to solve the universal migration problem.     

Use of sub-ambient DSC to complement conventional DSC and TG

Several drug substances or excipients are hygroscopic. The uptake or loss of water of such substances is generally difficult to control during processing or storage of drug products. DSC instruments with sub-ambient temperature equipment allow the determination of the amount of freezable water by measuring the corresponding melting enthalpy.The determination of freezable water adds valuable information complementary to TG analysis for understanding the processing and storage of raw materials and drug products. Several substances were tested as is, without treatment, after storage at 92% r.h. and after equilibration with water. The results of these experiments showed that it was possible to demonstrate defined hydrate formation, to determine the upper level of binding of water in amorphous substances and to confirm reversible hydrate formations demonstrated by temperature resolved X-ray diffraction.