Backbone chemistry

Propenylphenoxy compounds have attracted much research. BMI—propenylphenoxy copolymer properties can be tailored through modification of the backbone chemistry of the propenylphenoxy comonomer. Epoxy resins may react with propenylphenol (47,48) to provide functionalized epoxies that may be low or high molecular weight, Hquid or soHd, depending on the epoxy resin employed. Bis[3-(2-propenylphenoxy)phthalimides] have been synthesized from bis(3-rutrophthalimides) and o-propenylphenol sodium involving a nucleophilic nitro displacement reaction (49). They copolymerize with bismaleimide via Diels-Alder and provide temperature-resistant networks. 

Toughening of BMIs with thermoplastics is a promising approach however, more information is required about the toughening mechanism involved in order to select the most promising polymers in terms of backbone chemistry, molecular weight, and reactive groups. 

Fig. 35. Effect of backbone chemistry and molecular weight on Thermal Oxidative Stability (TOS) in air at 343 °C...

In addition to the Bisphenol-A backbone epoxy resins, epoxies with substituted aromatic backbones and in the tri- and tetra- functional forms have been produced. Structure-property relationships exist so that an epoxy backbone chemistry can be selected for the desired end product property. Properties such as oxygen permeability, moisture vapor transmission and glass transition temperature have been related to the backbone structure of epoxy resins5). Whatever the backbone structure, resins containing only the pure monomeric form can be produced but usually a mixture of different molecular weight species are present with their distribution being dictated by the end-use of the resin. 

Fig. 10.2 Stability of various oligonucleotide chemistries in the rat intestine prior to absorption. P=S designates phosphorothioate ASO backbone chemistry.

Figure 1. Dielectric constant vs. backbone chemistry for 6FDA/BDAF/PPD copolymers.

Polyorthoesters (POEs) are hydrophobic, surface-eroding polymers that have three g inal ether bonds that are acid-sensitive but stable to base. Like polyacetals, control of POE backbone chemistry allows for the synthesis of polymers with varied acid-catalyzed degradation rates and material properties. Fignre 30.4i d onstrates the molecular structure of POE. 

PALS results allow a comparison of the effect of polymer substituent and backbone chemistry on the relative size and concentration of free volume elements. The methane solubility is not strongly correlated with the PALS free volume parameters (similar to the result shown for fractional free volume in Figure 6a). The methane diffusivity and permeability of these polyisophthalamides are strongly... 

Thermotropic polyester backbone chemistry is characterized by a high degree of aromaticity, planarity, and linearity in the chain backbone. Most common moieties are p-phenylene, 1,4-biphenyl, and 2,6-naphthalyl moieties linked by ester or amide linkages. Polymers that form liquid crystal phases in the melt are thermotropic, whereas those that form liquid crystalline phases in solution are lyotropic. The all-aromatic polyester homopolymers tend to be intractable, decomposing at temperatures well below their melting points and insoluble in most... 

To understand the reasons for different predictions of different methods, Li et al. [83] measured the adhesion between a variety of polymers with well-controlled backbone chemistry These polymers include poly (4-methyl 1-pentene) [TPX], poly(vinyl cyclohexane) [PVCH], polystyrene [PS], poly(methyl methacrylate) [PMMA], and poly(2-vinyl pyridine) [PVP], poly(4-tert-butyl styrene) [PtBS], poly(acrylonitrile) [PAN], poly(p-phenyl styrene) [PPPS], poly(vinyl benzyl chloride) [PVCB]. It may be noted that, among the polymers listed above, TPX and PVCH are purely dispersive in nature. PS is predominantly dispersive with some dipole-induced dipole interactions. 

Phenolic resoles provided the backbone chemistry for the first structural adhesives for bonding metal substrates these were the Redux (/Jesearch at Dnxford) range of adhesives. They are invariably supplied as solutions, usually in industrial methylated spirits or ethanol, which effectively precludes their use in hot melt adhesive formulations. 

S. Sundaram, L. K. Lee and C. M. Roth, Interplay of polyethylenei-mine molecular weight and oligonucleotide backbone chemistry in the dynamics of antisense activity. Nucleic Acids Res., 35, 4396-4408... 

Other attempts to enhance lateral interactions via interchain interaction rely on the addition of copol5rmer imits able of hydrogen bond formation in two directions rather than on changing the p>ol5rmer backbone chemistry. The most successful attempt at present... 

There are many formulations, based on a large variety of backbone chemistries, which can be used as adhesives. As indicated above, apart from a few... 

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