Pendent group

Fig. 28. Traditional duv-resist design using derivatives of polyhydroxystyrene. Monomer (a) contributes hydrophilic character to the polymer, and its acidic phenol group enhances aqueous base solubiUty monomer (b) provides acid-labile pendent groups.

A number of thermally stable polymers have been synthesized, but in general the types of stmctures that impart thermal resistance also result in poor processing characteristics. Attempts to overcome this problem have largely been concentrated on the incorporation of flexible groups into the backbone or the attachment of stable pendent groups. Among the class of polymers claimed to be thermally stable only a few have achieved technological importance, some of which are polyamides, polyimides, polyquin oxalines, polyquinolines, and polybenzimidazoles. Of these, polyimides have been the most widely explored. 

Methacrylate monomers do not generally polymerize by a cationic mechanism. In fact, methacrylate functionaUty is often utilized as a passive pendent group for cationicaHy polymerizable monomers. Methacrylate monomers also have been used as solvents or cosolvents for cationic polymerizations (90,91). 

All phosphoms oxides are obtained by direct oxidation of phosphoms, but only phosphoms(V) oxide is produced commercially. This is in part because of the stabiUty of phosphoms pentoxide and the tendency for the intermediate oxidation states to undergo disproportionation to mixtures. Besides the oxides mentioned above, other lower oxides of phosphoms can be formed but which are poorly understood. These are commonly termed lower oxides of phosphoms (LOOPs) and are mixtures of usually water-insoluble, yeUow-to-orange, and poorly characteri2ed polymers (58). LOOPs are often formed as a disproportionation by-product in a number of reactions, eg, in combustion of phosphoms with an inadequate air supply, in hydrolysis of a phosphoms trihahde with less than a stoichiometric amount of water, and in various reactions of phosphoms haUdes or phosphonic acid. LOOPs appear to have a backbone of phosphoms atoms having —OH, =0, and —H pendent groups and is often represented by an approximate formula, (P OH). LOOPs may either hydroly2e slowly, be pyrophoric, or pyroly2e rapidly and yield diphosphine-contaminated phosphine. LOOP can also decompose explosively in the presence of moisture and air near 150° C. 

Fig. 2. Molecular structures of selected photoconductive polymers with pendent groups (1) poly(A/-vinylcarba2ole) [25067-59-8] (PVK), (2) A/-polysiloxane carbazole, (3) bisphenol A polycarbonate [24936-68-3] (4) polystyrene [9003-53-6] (5) polyvin5i(l,2-/n7 j -bis(9H-carba2ol-9-yl)cyclobutane) [80218-52-6]...

Fig. 3. Mechanisms for polymer degradation. The illustration is a schematic representation of three degradation mechanisms I, cleavage of cross-links II, hydrolysis, ionisa tion, or protonation of pendent groups III, backbone cleavage. Actual biodegradation may be a combination of these mechanisms.

Nonconjugated diene residual unsatuiation from the diene is in the pendent group. 

Mathias et al. synthesized poly(ether sulfone)s and poly(ether ether ketone)s with pendent adamantane groups.192 Incorporating adamantane into a polymer as a pendent group has been demonstrated to significantly increase the glass transition temperature. 

Polymers conjugated with 1-adamantyl moieties as lipophilic pendent groups can be utilized to design nanoparticulate dmg delivery systems. Polymer (1) in Fig. 26, which is synthesized by homopolymerization of ethyladamantyl malolactonate, can be employed as highly hydrophobic blocks to construct... 

Novel chiral. separations using enzymes and chiral surfactants as carriers have been realized using facilitated transport membranes. Japanese workers have reported the synthesis of a novel norbornadiene polymeric membrane with optically active pendent groups that show enantio.selectivity, which has shown promi.se in the. separation of propronalol. 

Actually, C-substituted cyclams are more common in the coordination chemistry of Co, with ligating pendent groups typically attached to the trimethylene ring C atoms. The synthetic... 

Capsules are instantly formed by simple addition of two equivalents of Pd(dppp)(OTf)2 (dppp = l,3-bis(diphenylphosphino)propane) to acetone, CH2C12 or CHC13 solutions of resorcin [4]arene derivatives having four pyridine units as pendent groups, see Figure 64.637... 

A. Polymers Containing Boron Atoms in the Backbone or in Pendent Groups... 

Carborane-containing polymers may be conveniently divided into two broad classes (1) polymers incorporating carboranyl fragments within the pendent group attached to the main chain, and (2) polymers containing carboranyl fragments within their main chain. 

A typical synthetic route to the incorporation of pendent carboranyl units into a polymer chain is shown in scheme 3. Poly(o-carboranyl-organo-siloxane)s have been successfully prepared through hydrolysis of dimethyldichlorosilane in the presence of carboranedichloromethylsilane. The polymer has some of the elastomeric characteristics of the parent poly(siloxane) however, the thermal-oxidative cleavage of the o-carboranyl pendent group is reported to occurat lower temperatures than that for the thermooxidative cleavage of Si—O and Si—C bonds.10 Thermal studies have... 

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