Acetal-protected poly

In this paper we report a new chemically amplified deep UV photoresist system based on acetal-protected poly(vinylphenoIs) and a photoadd generator. 

The system based on acetal-protected poly(vinylphenols) has the advantages that most chemically amplified photoresists have demonstrated, such as high sensitivity as the result of catalytic nature of deprotection reaction. However, the novel design of the system based on poly[4-(l-phenoi ethoi )styrene] shows several other advantages also. The imaging chemistry of fiiis system is illustrated in Scheme 2. 

Figure 4. Scanning Electron Micrograph of Positive Image of the Acetal-protected Poly(vinylphenol) 15 mJ/cm of 254 nm Radiation and Baked at 95 C for 2 Minutes.

Aldol group transfer polymerization of ferf-butyldimethylsilyl vinyl ether [62] was initiated by pendant aldehyde functions incorporated along a poly(methyl methacrylate) (PMMA) backbone [63]. This backbone was a random copolymer prepared by group transfer polymerization of methyl methacrylate (MMA) and acetal protected 5-methacryloxy valeraldehyde. After deprotection of the aldehyde initiating group, polymerization proceeded by activation with zinc halide in THF at room temperature. The reaction led to a graft copolymer with PMMA backbone and poly(silyl vinyl ether) or, upon hydrolysis of the ferf-butyldimethylsilyl groups, poly(vinyl alcohol) branches. 

Hydrolysis of trimethylsilyl (TMS) ether [129,130] and alcoholysis of a tetrahy-dropyranyl (THP) [131,132] group have been also employed in acid-catalyzed conversion to PHOST (Fig. 24) (or novolac). Another acetal-protected PHOST, poly[4-(l-phenoxyethoxy)styrene], was prepared by radical polymerization of the corresponding monomer and also by chemical modification of PHOST [133]. This acetal polymer produces a phenolic polymer and phenol upon aci-dolysis (Fig. 24). 

Acetal and ketal-protected poly(hydroxy styrene)-based resists... 

The concept of acid labile crosslinked units in polymers for positive DUV resist was evaluated with poly-(4-hydroxystyrene/4-vinylcyclohexanol) and implemented on a poly-4-hydroxystyrene backbone. The principle to increase the molecular weight by a transacetalization reaction was used to improve acetal protected phenolic resins for advanced chemically amplified resists. The polymer chains were linked via diols with acetal bridges. This type of linkage can be applied to a wide range of phenolic polymer binders. Resolution and thermal stability of the photoresist patterns were improved. Gel permeation chromatography and dissolution rate measurements prove that the crosslinked units remain essentially intact in the unexposed areas, thus enhancing... 

Suzuki A, Yano M, Saiga T, Kikuchi K, Okaya T (2003) Study on the Initial Stage of Emulsion Polymerization of Vinyl Acetate Using Poly(vinyl alcohol) as a Protective Colloid. Colloid Polym. Sci. 281 337-342. 

Other types of functionalized poly(3-alkylthiophene)s can be prepared in order to obtain polymeric materials with different chemical, optical, and electronic properties and different solubilities. The organozinc route has been used to synthesize poly thiophenes bearing a phosphonic ester functionality or functional groups such as bromine, ester, alcohol, and acetal-protected aldehyde as terminal groups of C-3-substituents, as illustrated in Scheme 11 [76]. 

Aldehydes can be protected as N,N-acetals, which are stable to highly basic reagents such as RLi. Therefore, the aldehyde function of 14 was treated with N,N -dimethylethylenediamine to convert it to a N,N-acetal-protected styrene (14e). ° Unlike the oxygen analogues, 14e was anionically polymerized without problem to afford a living polymer, which was stable in THF at -78 °C even after 24 h (Table 3). The protective group was quantitatively removed by acid hydrolysis with 2 N HCl in THF (Scheme 8). The SEC trace of the poly(14) thus obtained... 

The acetal-protected monomer, (2,2-dimethyl-1,3-dioxolan-4-yl)methyl methacrylate (32a), whose two hydroxyl functions were protected as a cyclic acetal, enabled the living anionic polymerization in THF at -78 °C with 1,1-diphenyl-3-methylpentyllithium/LiCl (Figure 35 and Table 10). The cyclic acetal-protected functionality was cleaved by treatment with 1 N HCl, quantitatively yielding water-soluble poly (2,3-dihydroxylpropyl methacrylate) (poly(32)) (Scheme 25). 

The same chemistry was used by Maynard and coworkers in a reverse way to immobilize biomolecides on antifouling PEG surfaces [43]. In their approach, acetal-protected aldehydes as chain ends of siuface-bonded poly(3,3 -diethoxypropyl methacrylate) were partially deprotected by irradiation with UV light (Scheme 22). Subsequently, the free aldehydes reacted with V-(aminooxyacetyl)-lV -(D-biotinoyl) hydrazine (ARP). Afterwards, the sample was irradiated again to deprotect further aldehydes. These free aldehydes were then used for the additirMi of aminooxy-terminated PEG, which is well-known for its antifouling properties. In the same step, dye-labeled streptavidin was attached onto ARP. Afterwards, the streptavidin could be used to immobilize any biotinylated proteins. 

A chemically amplified deep UV photoresist system based on acetal chemistiy is reported. Acetal-protected pol vinylphenols) were prepared either by free radical polymerization of the monomers or chemical modification of poly(vinylphenol). In the presence of an add as a catalyst, the polymers thermally decomposed to aqueous base soluble po vinylphenol) and some small molecules. Therefore, the resists were formulated with the acetal-protected polymers and a photoadd generator such as triphei lsulfonium hex-afluoroantimonate. Positive-tone image could be resolved 1 exposing the resist film in deep UV region, post-baking, and developing in tetramethylam-monium hydroxide solutions. 

Alternately, the acetal-protected polymers have also been prepared by chemical modification on poly(vinylphenol) by reacting the polymer with vinyl ethers using PFTS as the catalyst. ile satisfactory results were obtained with chemical modification using methyl vinyl ether, the reaction with vinyl phenyl ether showed a low efficiency of blocking the phenolic groups as FT-IR studies indicated that the chemically modified polymer still showed some unprotected... 

Emulsion Adhesives. The most widely used emulsion-based adhesive is that based upon poly(vinyl acetate)—poly(vinyl alcohol) copolymers formed by free-radical polymerization in an emulsion system. Poly(vinyl alcohol) is typically formed by hydrolysis of the poly(vinyl acetate). The properties of the emulsion are derived from the polymer employed in the polymerization as weU as from the system used to emulsify the polymer in water. The emulsion is stabilized by a combination of a surfactant plus a coUoid protection system. The protective coUoids are similar to those used paint (qv) to stabilize latex. For poly(vinyl acetate), the protective coUoids are isolated from natural gums and ceUulosic resins (carboxymethylceUulose or hydroxyethjdceUulose). The hydroHzed polymer may also be used. The physical properties of the poly(vinyl acetate) polymer can be modified by changing the co-monomer used in the polymerization. Any material which is free-radically active and participates in an emulsion polymerization can be employed. Plasticizers (qv), tackifiers, viscosity modifiers, solvents (added to coalesce the emulsion particles), fillers, humectants, and other materials are often added to the adhesive to meet specifications for the intended appHcation. Because the presence of foam in the bond line could decrease performance of the adhesion joint, agents that control the amount of air entrapped in an adhesive bond must be added. Biocides are also necessary many of the materials that are used to stabilize poly(vinyl acetate) emulsions are natural products. Poly(vinyl acetate) adhesives known as "white glue" or "carpenter s glue" are available under a number of different trade names. AppHcations are found mosdy in the area of adhesion to paper and wood (see Vinyl polymers). 

In poly(vinyl acetate) copolymer emulsions, the properties are significantly affected by the composition of the aqueous phase and by the stabilizers and buffers used iu the preparation of these materials, along with the process conditions (eg, monomer concentrations, pH, agitation, and temperature). The emulsions are milk-white Hquids containing ca 55 wt % PVAc, the balance being water and small quantities of wetting agents or protective coUoids. 

Poly(vinyl acetate) emulsions can be made with a surfactant alone or with a protective coUoid alone, but the usual practice is to use a combination of the two. Normally, up to 3 wt % stabilizers may be included in the recipe, but when water sensitivity or tack of the wet film is desired, as in some adhesives, more may be included. The most commonly used surfactants are the anionic sulfates and sulfonates, but cationic emulsifiers and nonionics are also suitable. Indeed, some emulsion compounding formulas require the use of cationic or nonionic surfactants for stable formulations. The most commonly used protective coUoids are poly(vinyl alcohol) and hydroxyethyl cellulose, but there are many others, natural and synthetic, which are usable if not preferable for a given appHcation. 

Poly(vinyl acetate) emulsions are excellent bases for water-resistant paper adhesives destined for use in manufacturing bags, tubes, and cartons. Glue-lap adhesives, which require moderate-to-high resistance to water, exemplify this type. When routine water resistance is required, a homopolymer vinyl acetate emulsion containing a ceUulosic protective coUoid is effective for most purposes. Next effective are emulsions containing fuUy hydrolyzed poly(vinyl alcohol) as a protective coUoid, foUowed by those containing partiaUy hydrolyzed poly(vinyl acetate). 

Poly(vinyl acetate) latex paints are the first choice for interior use (149). Their abihty to protect and decorate is reinforced by several advantages belonging exclusively to latex paints they do not contain solvents so that physiological harm and fire ha2ards are eliminated they are odorless they are easy to apply with spray gun, roUer-coater, or bmsh and they dry rapidly. The paint can be thinned with water, and bmshes or coaters can be cleaned with soap and tepid water. The paint is usually dry in 20 minutes to two hours, and two coats may be applied the same day. 

Poly(vinyl chloride-i o-vinyl acetate) [9003-22-9] has found appHcation in flooring, phonograph records, protective coatings, fibers, and some films and sheeting. Because of their low viscosity and good processabihty, such copolymers constitute the bulk of the vinyl tile market. The total production of PVC copolymers in 1989 was 113,500 t (73) (see Vinyl polymers). 

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