Hydrolytically Stable Monomers

These trends were attributed to a strong interaction of the PA groups with HAP. Although such materials exhibited weak adhesion properties, they clearly showed the great potential of PAs in dental materials. Over the past decades, the development of new PA monomers for use in dental materials has attracted much attention. An overview of the PA methacrylates and oc-substituted acrylates developed for dental applications will first be provided. Then, we will focus our attention on the preparation of hydrolytically stable monomers. 

Lack of hydrolytically stable monomers with a suitable selectivity for bromate/ chloride and bromide/chlorate/nitrate separations. 

It has been reported that the effectiveness of copolymerized DOPO-type monomers can be further improved if the alcohol-amine derivatives of DOPO, for example, Structure 5.11, are used rather than similar structures not containing nitrogen.30 Of the FR fibers based on P-containing comonomers, it has been found that those based on Structure 5.10 are more hydrolytically stable, presumably because the P-containing group is in a cyclic structure and also should the hydrolysis of the P-0 bond occur, it will not lead automatically to a marked reduction in molecular weight.31 All the P-modified PETs appear to be subject to both the vapor-and condensed-phase mechanisms of flame retardance, with the former predominating.32 33... 

Acrylates. Acrylamines are widely used to create polymeric coatings on fused silica capillaries in a two- to three-step process. Linear polyacrylamide is then grafted to the appropriately prepared surface. The problem of acrylamide stability can be solved by using a monomer that is inherently more hydrolytically stable. 

The propellants derived from nitrate ester-based binders possessed the undesirable characteristics associated with nitrate ester groups such as thermal instability, hydrolytic instability, and impact instability (especially for highly nitrated compositions). For this reason a study was undertaken to prepare polymeric binders in which oxygen is carried in the form of the more thermally and hydrolytically stable nitro group. Aerojet General Corp., working with both the Purdue and the Ohio Research Foundations, carried out the bulk of these studies. The following are typical of the condensation monomers synthesized by Aerojet ... 

Azide Derivatives. Azidoformates are prepared from a hydroiC yl - Containing monomer via the chloroformate and sodium azide. Cenerally hydrolytically stable, they can be used either in cdreot copolymerisation or as post - additives, functioning by a secondC ary reaction. In the latter case the reaction is not restricted to azoformates of polymerisable acids. The crosslink at 70 prodC uoes a urethance type linkage. 51)... 

Statistical copolymers were reported for N-vinylimidazole and 13b [50], for acrylamide with 9a [11], 9b [12], and 9c [13], and for terpolymers of acrylamide, sodium acrylate, and 9b [51]. Several hydrolytically stable am-monioacetate and pyridiniocarboxylate monomers based on isobutylene with variable length of hydrophobic side chains did not homopolymerize, but these monomers with surfactant properties are suited for copolymerization with electron-poor monomers [52]. 

In recent years, there have been significant developments in the field of living carbocationic polymerization (LCCP) of vinyl monomers, such as isobutylene (IB), styrene and its derivatives, and vinyl ethers, leading to a wide variety of functional polymers (for recent reviews see Refs. 1-4). Due to the attractive properties of polyisobutylene (PIB) available only by carbocationic polymerization, coupling this hydrophobic, thermally, oxidatively, and hydrolytically stable polymer with a low Tg to a variety of other chain segments is expected to result in new useful products. For instance, methacrylate-telechelic PIB (MA-PIB-MA) obtained by LCCP and subsequent chain end derivatization has been successfully used to synthesize novel amphiphilic networks by radical copolymerization of MA-PIB-MA with a variety of monomers, such as N,N-dimethylacrylamide and 2-trimethylsilyloxyethyl methacrylate, a protected 2-hydroxyethyl methacrylate... 

Silicon-containing epoxides with hydrolytically stable carbon-silicon bonds were first prepared by Pleuddeman by the addition of hydrogen functional silanes to epoxy compounds containing double bonds (7,8). We have employed this reaction extensively to prepare several different difunctional epoxy monomers as shown in Table I. An example of this reaction is given in equation 1 for the preparation of difunctional monomer HI. 

Chapter 2 by Monge et al. details the synthesis and polymerization of phosphorus-containing (meth)acrylamide monomers. Compared to their (meth)aciylate homologues, this class of monomer is more hydrolytically stable and thus more interesting for a large variety of applications. Nevertheless, these monomers are less studied and most of the results mainly report their photopolymerization in order to develop stable self-etching dental primers. Future research on phosphorus-based (meth)acrylamide monomers is also discussed in this chapter and specifically the synthesis of block copolymers by controlled radical polymerization is investigated. 

Furthermore, we synthesized DHP-6, a crosslinking monomer containing an undecamethylene spacer. Unfortunately, this monomer did not show any improved performance compared to DHP-4 or DHP-5. We also took an interest in the synthesis of O-alkylated acrylic acid hydroxamides, such as the 10-(iV-acryloyl-iV-metho>yamino)decyl dihydrogen phosphate DHP-7. However, these monomers were less hydrolytically stable compared to the corresponding (meth)acrylamides. Over the last few years, several... 

Moisture resistance This may be increased on metal and glass substrates by including cross-linking agents, which may yield a more hydrolytically stable polymer or by using hydrophobic monomers such as fluorinated cyanoacrylates. Silane adhesion promoters also improve moisture durability. There is also evidence to suggest that inclusion of some of the anhydrides described above has a beneficial effect. 

Acrylamido-2-methylpropanesulfonic acid (AMPS) n. A solid aliphatic sulfonic-acid monomer produced by Lubrizol Corp. Its homopolymers are water-soluble and hydrolytically stable. It can be incorporated into other polymers by crosslinking. 

In contrast to the poly(enamine-ketones) prepared by Imai e al. the methyl substituted poly(enamine ketones), J 2, prepared from the condensation of diamines and bis-acetylacetylarenes, were found to be hydrolytically stable and thermally stable from 257 to 340 C, When a linear and rigid aromatic bis(1,3-diketone) was condensed with alkaline dieamines with ten or more carbons or with rigid aromatic diamines, thermotropic liquid crystalline materials were obtained. The monomers and polymers have much higher solubilities and lower transition temperatures as compared with liquid crystals containing only aromatic hydrocarbon rings of similar structures. 

Other Sulfonic Acids. Extensive development work has been conducted on acrylic sulfonate-containing monomers. 2-Sulfoethyl methacrylate (SEM) monomer 5Ahas proved to be of limited commercial value owing to the hydrolytic instability of the ester linkage. However, recently well-defined homopolymers of 3-sulfopropyl methacrylate (SPMA) were prepared under aqueous RAFT conditions with 4-cyanopentanoic acid dithiobenzoate and V-501 as the CTA/initiator pair at 70°C (39). This same hydrolytic instability has been a serious problem with 3-sulfo-2-hydroxypropyl methacrylate. In contrast, 2-acrylamido-2-methylpropanesulfonic acid (AMPSA) 6A, prepared by the reactions of SO3 with isobutylene followed by the Ritter reaction with acrylonitrile (134), is quite hydrolytically stable. 

In the synthesis of hydrolytically stable, crystalline poly(L-lactic acid), (PLLA), the choice of catalyst and reaction conditions are important to minimize the extent of racimization [22-23], which could lead to a decrease in properties. Also maximizing the molecular weight while minimizing the unreacted monomer has been shown to be important for the synthesis of poly(L-lactic acid) with longer in vivo strength retention [24]. 

Similar to MOFs but constructed of organic monomer units are POPs. These promise to be more thermally and hydrolytically stable than... 

Through proper design of backbone monomer composition and the use of a more hydrolytically stable amide linkage to the hydrophobic functionality, thermally stable hydrophobically associating polymers can be obtained. This is another area worthy of further study. 

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