Methylene-1,4-phenylene

Poly(anhydrides) are polymers containing the group -C(0)-0-C(0)- in their backbone. Several polyanhydrides such as poly(oxyisophthaloyl), poly(oxycarbonyl-1,4-phenylene methylene-1,4-phenylene carbonyl), poly(oxycarbonyl-1,4-phenylene isopropylidene-1,4-phenylene carbonyl), and poly(oxycarbonyl-1,4-phenylene isobutylidene-1,4-phenylene carbonyl) were synthesized with the expectation of good biodegradability. They do have good hydrolytic stability as opposed to aliphatic polyanhydrides [1]. The structures of these polymers are shown below. 

Aromatic diisocyanates such as toluene 2,4-diisocy-anate (TDI) and methylene di-p-phenylene isocyanate (MDl) are usually used. Aliphatic diisocyanate such as hexanediisocyanate (HDI), although it has the advantage that the TPU synthesized from it is softer and not prone to turning yellow, is seldom used due to its high cost. 

B. m-Phenylene-diisocyanate, toluenediisocyanate. xylenediisocya-nate, butylated hydroxytoluene, 5-chlorotoluenediisocyanate, and methylene-bis-(4-cyclohexylisocyanate)... 

Poly(epichlorohydrin) (PECH) and poly(2,6 - dimethyl-1,4-phenylene oxide) (PPO) containing pendant mesogenic units separated form the main chain through spacers of zero to ten methylene units were synthesized and characterized in order to test the "spacer concept." Both polymers were modified by phase transfer catalyzed esterifications of the chloromethyl groups (PECH) or the bromobenzyl groups (brominated PPO) with potassium co -(4-oxybiphenyl) alkanoates and potassium u-(4-methoxy-4-oxybiphenyl)-alk.an oates. While PPO required ten methylene units as a spacer and 4,4 -methoxybiphenyl as mesogen to present thermotropic liquid crystalline mesomorphism,... 

In order to determine the necessity and/or the length of the spacer that is required to achieve liquid crystalline behavior from flexible vs. rigid polymers, we have introduced mesogenic units to the backbones of a rigid [poly(2,6-dimethyl-l,4-phenylene oxide) (PPO)] and a flexible [poly(epichlorohydrin) (PECH)] polymer through spacers of from 0 to 10 methylene groups via polymer analogous reactions. 

Sediment Trap hydrogen sulfide in sodium hydroxide sulfide reacts with AW-dimethyl-p-phenylene-diamine to from methylene blue. Colorimetry 0.01 pmol/gram NR Allen et al. 1994... 

Acetylene dicarboxylate and maleic anhydride failed to react with simple methylene cyclopropenes, but reacted readily with calicene derivatives, as shown by Prinz-bach293. Thus ADD combined with benzocalicene 497 to give the dimethyl tri-phenylene dicarboxylate 499, whose formation can be rationalized via (2 + 2) cycloaddition across the semicyclic double bond as well as (4 + 2) cycloaddition involving the three-membered ring (498/501). The asymmetric substitution of 499 excludes cycloaddition of ADD to the C /C2 triafulvene bond (500), which would demand a symmetrical substituent distribution in the final triphenylene derivative. 

In a pyrogram of Bisphenol A poly(formal) (6), the peak products are identified as a-methylstyrene, phenol, 4-hydroxy-a-methylstyrene, and isopropyl phenol by Py-GC/MS. These products are identical with the degradation products from Bisphenol A. In addition to the decomposition products of Bisphenol A, 4-isopropenyl anisole is also identified as a product. The pyrograms of Bisphenol AF poly(formal) (7) contain only two major species, pentafluoroisopropenyl benzene (product T) and pentafluoroisopropenyl anisole (product 2 ). They correspond to a-methylstyrene, 4-hydroxy-amethylstyrene from Bisphenol A poly(formal) (6) and are produced by the cleavage of phenylene-oxy bonds and oxy-methylene bonds according to (Scheme 6). 

Preparation of poly(m-phenylene)iso/terephthalate (80/20). The polymers were prepared by solution condensation of the acid chlorides with resorcinol in methylene chloride solution using triethyl amine as the acid acceptor as described by Korshak (10). 

Preparation of Polymer Blends. A series of polymer blends was prepared by co-solutioning predetermined amounts of the poly(m-phenylene)isophthalate/terephthalate (80/20) with poly (m-phenylene)phenyl phosphonate, in methylene chloride. The polymer blends were recovered by evaporating the solution to dryness and ground to 40 mesh with a Wiley Mill. The composition of these blends and their analyses are summarized in Table I. 

Methylene Chloride Fractionation of Cross-Coupled 1. 2 and 7. A sample of the block polymer (above 0.50g) was dissolved in 10 mL of methylene chloride. The soluton was stored at 2 C for 2 days. A polymer methylene chloride complex precipitate formed which was removed by filtration at 2aC. The precipitate was then heated at 50 to drive off the methylene chloride. The dried polymer weighed 0.43g and contained (based on IR analysis) 58% by weight of poly(phenylene oxide) and 42% by weight of polystyrene. Analysis of the filtrate after evaporation of the methylene chloride established the presence of a residue containing 17% polyphenylene oxide and 83% polystyrene. On the basis of these results, at least 72% of the initial polystyrene charged to the reaotion medium was calculated as having been incorporated into an acyl-coupled polyphenylene oxide-polystyrene block polymer. 

PMPPIC Poly(methylene) poly(phenylene) isocyanate... 

These derivatives are soluble in an acetone/water mixture with their p i values similar to that of PIDAA. The phenylene analogs are similar to EDTA except that the two nitrogens are bridged by aromatic rings. These derivatives are soluble in acetone/water. They were characterized by measuring their H- and C-nuclear magnetic resonance (NMR) spectra and Fourier transform infrared (FTTR) spectra. All the PIDAA derivatives showed a peak near 53 ppm for the methylene carbons in carbon NMR spectra. The methylene carbon resonance appears around 44 ppm in the NPG derivative. Thus offers an easier way to characterize these materials. The FTNMR data are listed in Table 1 below. 

The fast electron transfer mentioned for the p-phenylene-linked system results in the transfer of the three-electron two-nitrogen unit from one-hydrazine ring to the other. Such superexchange transfer is a specific phenomenon. As found by Nelsen and Ismagilov (1999), this bis(hydrazine) cation-radical is significantly ion paired with PFg counterion in the methylene chloride solution. The counterion touches both hydrazine fragments, but the distance between the N.-.N linkage and PFg is permanently shorter than that between N—N and PFg . 

The simplest motional description is isotropic tumbling characterized by a single exponential correlation time ( ). This model has been successfully employed to interpret carbon-13 relaxation in a few cases, notably the methylene carbons in polyisobutylene among the well studied systems ( ). However, this model is unable to account for relaxation in many macromolecular systems, for instance polystyrene (6) and poly(phenylene oxide)(7,... 

The reaction of iV-phenyl-o-phenylenediamine (10) with DMAD gives a mixture of products consisting of l-phenyl-2-oxo-3-carbomethoxy-methylene-l,2,3,4-tetrahydroquinoxaline (11) and l-phenyl-2,3-dicarbo-methoxy-l,2,3,4-tetrahydroquinoxaline (12) [Eq. (4)]. m-Phenylene-diamine and p-phenylenediamine give the corresponding bisenamines 13... 

The Tm of condensation polymers such as polyesters and polyamides is decreased as the number of methylene (CHj) groups in the reactants is increased. The presence of stiffening groups, such as phenylene groups in a polymer chain, increases the Tm. 

As in the case of nylons, the flexibility of PUs is increased as the number of methylene groups is increased, and the rigidity is related to the number of stiffening groups, such as phenylene groups in the chain. As the number of methylene units increases (Table 14.6), the Tm decreases. The Tm generally increases as the flexible units are replaced by nonflexible units, such as phen-ylenes and piperazines. Thermal and physical properties of aliphatic PUs are shown in Table 14.7. 

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