Chloromethyl group, sensitization

Proteins may be covalently attached to the latex particle by a reaction of the chloromethyl group with a-amino groups of lysine residues. We studied this process (17) using bovine serum albumin as a model protein - the reaction is of considerable interest because latex-bound antigens or antibodies may be used for highly sensitive immunoassays. The temperature dependence of the rate of protein attachment to the latex particle was unusually small - this rate increased only by 27% when the temperature was raised from 25°C to 35°C. This suggests that non-covalent protein adsorption on the polymer is rate determining. On the other hand. the rate of chloride release increases in this temperature interval by a factor of 17 and while the protein is bound to the latex particle by only 2 bonds at 25°C, 22 bonds are formed at 35°C. 

We note from Table VIII a strong interest in halogenated resists, particularly those substituted with chlorine. The addition of chlorine to the aromatic structure of polystyrene has a marked effect on cross-linking efficiency. Monodisperse polystyrene, for example, has a sensitivity on the order of 50 p C/cm2, yet with as little as 20% chloromethyl groups substituted on the ring, the sensitivity is improved to 2 C/cm2 for comparable molecular weight and distribution. 

We have developed a new silicone based negative resist (SNR) by introducing the chloromethyl group into polydiphenylsiloxane. SNR has a high Tg (170 C), good electron beam sensitivity and excellent durability to 02 RIE (9). In this paper we describe the SNR preparation and characteristics, and demonstrate a high resolution of 2LR system using this resist. 

Resists based on chloromethyl substitution have been extensively studied in the past few years (7-7). Halogen and halomethyl groups have been introduced by a variety of methods. Choong and Kahn (7) synthesized polychloromethylstyrene (PCMS) by free radical polymerization of chloromethylstyrene and reported a sensitivity (D 5) of 0.4 / 2 at 20 kV with a contrast of 1.5 for materials with molecular weight of about 400,000 (7). The molecular weight distribution of these polymers, all of which contained one chloromethyl group per repeat unit, was about 2. Fractionation of the polymer resulted in improved contrast as a result of narrowing the distribution. 

Sensitivity for calixarenes are comparatively low compared to today s standard electron resists. This is natural because small molecules require many cross-links per unit volume to make a gel state (17). To improve the sensitivity, a chloromethyl group was selected because its reaction is a step-wise reaction. Introducing a reactive group which undergoes a chain reaction, such as an epoxy group, or employing a di sion mechanism in resist reaction was deliberately avoided to maintain the high resolution capability of calixarenes (18,19). 

Another example of chlorine-enhanced sensitivity is with the use of pendant chloromethyl groups on aromatic rings. Poly(chloromethylstyrene) and chlorinated poly(p-methylstyrene) have been studied as e-beam resists and have been found to have good sensitivity to 4.36 A radiation. 

Polysiloxanes. The initial reports of the utility of polysiloxanes for lithographic applications spurred several research groups to further investigate this class of materials. The problem of low Tg was addressed by preparing chloromethylated poly(diphenylsiloxane) 16, 17). More recently, poly(sil-sesquioxanes) 18, 19) have been reported as sensitive, negative, e-beam, ion-beam, and UV resists. These soluble, ladder -type polymers prepared by the hydrolysis of substituted chloro- and alkoxysilanes are high-Tg materials (150 °C) with high silicon contents. 

A spirothietane sulfone-oxetane is a comonomer in the preparation of polyethers. A polymer obtained from this sulfone in a solution of bis(3,3-chloromethyl) oxetane with phosphorus pentafluoride can be spun to drawable filaments. Thietane sulfone spirocyclic carbonates may be polymerized via the carbonate group to high-molecular-weight solids said to be useful in laminating. Thietane 1,1-dioxide improves the dye receptivity of poly (acrylonitrile), viscose, cellulose acetate, and poly(vinyl chloride). It is also reported to be a stabilizer for nitric acid in oxidizer mixtures for rocket motors. 2-Methylthietane 1,1-dioxide is claimed to be superior to sulfolane (thiolane 1,1-dioxide) in the liquid extraction of aromatic hydrocarbons from mixtures with saturated hydrocarbons. " A number of bis(3,3-alkoxy) thietane 1,1-dioxides have been proposed as intermediates in the preparation of cyanine dyes useful as photographic sensitizers. " ... 

The chloromethyl imines lOa-lOi were employed as representatives of derivatives with a potentially reactive group in the side chain. Their reduction afforded the corresponding amines in >90% ee (Table 4.6, entries 1 9). The resulting amino chlorides were then cyclized to the corresponding aziridines on treatment with t BuO K with retention of the stereochemical integrity [ 12d]. It is pertinent to note that the preparation ofthe sensitive chloro imines lOa-lOi from the a chloro ketones was not entirely free of problems while the electron neutral and electron poor imines lOa-lOc were synthesized and isolated as individual substances, their electron rich counterparts lOg and lOh could not be obtained as pure compounds, since the reaction did not proceed to completion. Therefore, in the latter instances, the imines were generated in situ [12d]. 

In two closely related papers [40, 41] CP/MAS was used to examine a series of styrene-divinylbenzene (St-DVB) and chloromethylated resins. In the first part of this study the authors were concerned with trying to determine the residual amount of unreacted vinyl groups present in St-DVB resins (see Section 3). In order to increase the sensitivity of the method the authors used C -labelled divinylbenzene (labelled in the methine position) and combined this with unlabelled styrene (1-20% by weight). The final resins were examined by CP/MAS and it was found that even for a very lightly erosslinked... 

Reactions of Imidazoles. Thermolysis of 1-triphenylmethylimidazole results in migration of the imidazolyl group to yield compound (286). Sensitized photo-oxygenation of 4,5-diphenylimidazole in methanol affords a mixture of the imidazolinone (287) and the imidazolidinone (288). The imidazole (289 R = H) undergoes lithiation at C-5 subsequent treatment with diphenyl disulphide gives the di(phenylthio)-derivative (289 R = PhS). Copyrolysis of 2,4-dimethylimidazole and chloroform results in a complex mixture, containing imidazole and methyl-, dimethyl-, and chloromethyl-pyrimidines and -pyrazines. The confusion about the structures of N-methyl derivatives of iodo-nitro-imidazoles has been cleared up the supposed 1-methyl-2,5-di-iodoimidazole is actually the 4,5-di-iodo-compound it yields 4-iodo-l-methyl-5-nitroimidazole on nitration. The reaction of the bromo-... 

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