Aliphatic backbones

Bi- and poly-thioethers with aliphatic backbones are produced by attack of RS on the appropriate haloalkane. This is the method of choice for RS(CH2)raSR (R = Me or Ph),26 MeC(CH2SR)3,27,28 MeS(CH2)raS(CH2)raSMe (n = 2 or 3) and MeS(CH2)raS(CH2) S(CH2) SMe.28,29 [Caution Some of these syntheses involve sulfur mustard derivatives as intermediates - these are very powerful vesicants and should be handled only with extreme care.] The other tridentates RS(CH2)3S(CH2)3SR (R = Et, Pr or Ph) may be obtained from nucleophilic attack by RS on the ditosylate TsO(CH2)3S(CH2)3OTs.30 Tetra-dentate thioethers involving o-phenylene interdonor linkages are also known.31 More recently the preparation and coordination chemistry of the silicon-apex derivative MeSi(CH2SMe)3 has been described.32... 

In early work no such NMR chemical shift changes relative to those of the parent components were observed for polypseudorotaxanes with aliphatic backbones and aliphatic crown ethers as the cyclic species [108, 109]. Model studies were performed with 18-crown-6 (18C6), which is so small that it cannot be threaded. The recovery of intact 18C6 under conditions identical with those for the syntheses of the polyrotaxanes ruled out the possibility of side reactions. The effective removal of the small crown ether by precipitation into a solvent which was poor for backbone but good for the cyclic demonstrated the effectiveness of the purification procedure. In addition, reaching a constant min value after multiple precipitations and the absence of the peak for free crown ether in GPC traces indicated that the larger crown ethers detected by NMR in the purified polymeric products were indeed threaded rather than simply mixed. 

A waterborne system for container coatings was developed based on a graft copolymerization of an advanced epoxy resin and an acrylic (52). The acrylic—vinyl monomers are grafted onto preformed epoxy resins in the presence of a free-radical initiator grafting occurs mainly at the methylene group of the aliphatic backbone on the epoxy resin. The polymeric product is a mixture of methacrylic acid—styrene copolymer, solid epoxy resin, and graft copolymer of the unsaturated monomers onto the epoxy resin backbone. It is dispersible in water upon neutralization with an amine before cure with an amino—formaldehyde resin. 

Work in our group has been concerned with C2u-symmetrical ligands in which a central heterocycle carries four aliphatic side-arms (type I ligands) (5). In other cases, the donor set AE4 (A apical donor, E equatorial donor) has the same overall symmetry, but consists entirely of heteroaromatics (type II ligands). Thirdly, two ligands have so far been described which have overall Cs symmetry, in which the central , apical donor atom is part of an aliphatic backbone (type III ligands). 

Normally polymer structures containing aliphatic backbones are low in smokegenerating character and are generally not self-extinguishing. Additives to such systems to achieve flame-retardancy often enhances smoke generation Polymers with aromatic side groups such as polystyrene have a considerable tendency to generate smoke. 

Long aliphatic backbone monomer with good wetting properties. 

Another example is Dias Analytics styrenic membrane based on the well-known block copolymer styrene-ethylene/butylene-styrene family.This membrane has good conductivity 0.07 to 1.0 S/cm when fully hydrated. It showed reasonable performance but had poor oxidative stability due to the susceptibility of its aliphatic backbone to peroxide attack. 

The pre-polymers typically contain at least two epoxy groups spaced with an aromatic or aliphatic backbone or even by a fragment of chain including other functionalities. The most commonly used resin from this class is probably formed from epichlorohydrin and bisphenol A or 4-[1-(4-hydroxy-phenyl)-isopropyl]phenol under basic conditions to give a polymeric diglycidyl polyether as shown below ... 

The polyesters shown in Table 2 have repeating units consisting of 9 and 18 skeletal bonds, respectively, while the adipic acid-pentaerithritol polymer has a repeating unit of 11 bonds on the same sort of aliphatic backbone, an intermediate length of the polyesters shown in Table 2. Hence, Jones and coworkers experiment is a good measure for the present estimate. An only difference between... 

In an attempt to provide alternative supports to styrene-divinylbenzene resins [32] for use in reactive chemistry, poly(hydroxyethylmethylacrylate) (poly(HEMA)) has been employed. In this study poly(HEMA) was crosslinked with ethyleneglycol dimethacrylate and the CP/MAS recorded. The peaks were assigned as follows 18.6 ppm is due to the methyl attached to the aliphatic backbone 56.0 and 45.4 ppm are due to the methylene and quaternary of the backbone the —OCH2— forming the crosslink are at... 

The correction of +25 for a bromine atom directly attached to an aromatic backbone carbon atom is larger than the correction of +20 for a bromine atom attached to an aliphatic backbone atom or to any type of side group atom. 

Cyclopolymers having 13-membered rings as repeating units were obtained by cationic initiation of l,2-bis(2-ethenyloxyeth-oxy)benzene under the conditions shown in Eq. 7 and summarized in Table V. The polymer was soluble in essentially all common organic solvents but insoluble in water and petroleum ether. The absorptions of the vinyloxy group were completely absent in the IR spectrum of polymer JL3. The CMR showed complete absence of vinyloxy carbons, but saturated aliphatic backbone carbons appeared. The solubility and spectroscopic evidence is consistent with the proposed structure 13. 

The IR absorptions of the vinyloxy group at 1610 cm-i and 975 cm l were completely absent in the spectrum of polymer 13. Instead, peaks at 740 cm l and 1595 cm-l from benzene ring, 920, 1120 and 1260 cm-1 from C-0-C were observed. PMR spectra showed three peaks, aromatic protons at 6 6.9, protons of carbon adjacent to oxygen at 6 4.0 and saturated aliphatic protons at 6 1.80 but no vinylic protons at 6 6.2. The integration results agreed well with the numbers of different protons. CMR showed complete absence of vinyloxy carbons at 86.82 ppm, but the saturated aliphatic backbone carbons appeared at 40.91 ppm. 

Nonpolar C-C and C-H components of the polymer have a lower surface energy than the more polar C-N groups. Consequently the aliphatic backbone of the polymer will favor the surface, and the pyridine nitrogen atoms will tend to project away from the surface. 

Poly(vinyl acetate) consists of a 1,3-substituted aliphatic backbone with an acetate group at every second carbon atom in the chain. As a result, the polymer surface is hydrophobic and not wetted, swollen, or dissolved by water. However, in alkaline media the acetate groups can be partially or fully saponified to OH groups. The resulting structure is a poly(vinyl acetate-vinyl alcohol) copolymer, which becomes increasingly soluble with increasing degree of saponification. 

The second polymer under investigation is pure poly(vinyl alcohol), which is basically the product of full saponification of poly(vinyl acetate), and, thus consists of an aliphatic backbone with an OH group at every second carbon atom in the chain. The presence of this large amount of OH groups makes the polymer hydrophilic, i.e. the polymer surface is easily wetted by water. Upon contact with water, PVA readily swells and is then dissolved. 

Figures 4 and 5 present the heteronuclear correlation spectra for the diblock PCL-PS ICs with a- and y-CD, respectively, where it is apparent that the PS protons are not in close proximity to the host protons of a- or y-CDs. This clearly confirms that the PS blocks are excluded from the CD channels. At the same time, however, the PCL and CD protons are proximal, and at Xm = 10 ms nearly identical proton resonance frequencies are observed for both guest PCL blocks and host CDs due to spin diffusion between their nearby protons. Also note that the aliphatic backbone carbons (g) at -40 ppm show correlation to both the aliphatic and aromatic protons (h), which is possibly due to crosspolarization of the methine carbon by the ortho protons. There is clearly spin-diffusion between PS protons, but not between PS protons and the PCL or CD protons.

Recently, Gusev and coworkers [37] reported the PNN mthenium pincer complex 14 with an aliphatic backbone, which displayed impressive catalytic activity in the presence of a base (KO Bu, 0.5 mol%) for the conversion of simple alcohols such as ethanol and propanol. Although the reactions worked at temperatures below 100 °C, good conversions required heating at higher temperatures (Table 1.3,... 

---