Polyaryl derivatives

The liquid crystallinity and the moduli of as-spun fibers of polyarylates from substituted HQs and substituted PECs could be controlled by the substituents shown in Table 19.1. Polyarylates derived from /-butyl HQ (fBu-HQ) and PEC (fBu-HQ/PEC), and phenyl-HQ (Ph-HQ) and PEC (Ph-HQ/PEC), showed decreased liquid crystallinity when compared to chloro-HQ (Cl-HQ) and PEC (Cl-HQ/PEC), and methyl-HQ (Me-HQ) and PEC (Me-HQ/PEC), because of the bulky substituents on the HQ units. 

Polyarylates derived from various substituted HQs and l,2-bis(methoxy-phenoxy) ethane-4,4/-dicarboxylic acid or l,2-bis(2,6-dichlorophenoxy)ethane-4,4 -dicarboxylic acid exhibited low moduli because of the lack of liquid crystallinity resulting from the steric hindrance of the substituents on the PEC units. 

The Tm values of the poly(alkylene-4,4 -diphenyldicarboxylate)s are much higher than those of the poly(alkylene terephthalate)s. Therefore, as polyarylates derived from substituted HQs and BB seemed to have higher Tms, the, LCPs derived from BB and alkylene glycols with higher carbon numbers have been investigated [24],... 

However, in spite of the higher rigidity of the polymer chains, many pol-yarylates derived from substituted HQs and BB exhibited liquid crystallinity and lower Tms when compared to the polyarylates derived from substituted HQs and TA. 

However, as-spun fibers of the polyarylates derived from Me-HQ and BB (Me-HQ/BB) exhibited a lower modulus than that of Me-HQ/Cl-PEC in spite... 

The glass transition temperatures (Tgs) of polyarylates derived from substituted HQs and substituted PECs are shown above in Table 19.1. Polyarylates containing bulky substituents, such as / Ifu, on the HQ units exhibit above high glass transitions due to the high rigidity of their molecular structures. Thus, fBu-HQ/PEC shows a high Tg of 146 °C when compared to that of Me-HQ/PEC (104 °C). 

Polyarylates derived from BB show a high 7 g, while their HDT values depend upon both the Tt and the crystallinity. 

We expected that polyarylates derived from 4,4 -diphenyl-dicarboxylic acid(BB) would show increased stability of the liquid crystalline state compared with PEC due to the longer mesogen unit,but at the same time,we were afraid that melting temperatures(Tms) of these polyarylates would be very high because Tm of poly(ethylene 4,4 -diphenyldicarboxylate) was much higher than that of poly(ethylene terephthalate) and poly(methylhydroquinone terephtalate)(Me-HQ/TA) showed no liquid liquid crystallinity even at the temprature above 450 C. 

In order to obtain high modulus as-spun fibers,the stability of liquid crystalline state and the rigidity of polymer chain are influential factors.Therefore,we expected that the polyarylates derived from BB would show higher modulus than those from PEC or Cl-PEC.As-spun fiber of the polyarylate derived from Cl-HQ and BB modified with TA(Cl-HQ/BB/TA) showed the modulus of 95 GPa(m/n= 7/3) which was higher modulus compared with that of Me-HQ/Cl-PEC. However,as-spun fiber of Cl-HQ/BB/TA showed the modulus of only 11 GPa(m/n=8/2) in spite of the rigid chemical structure,and this is referred to the decreased elongational flow orientation as shown in Fig. 4(3). 

The density of the injection molded test pieces of polyarylates derived from BB was low.The density of Me-HQ/BB/NDA(m/n=9.5/0.5) was 1.3. We assumed that the reason of the low density was the twisted structure of biphenylene unit(4). 

Fiordeliso, J. (1993) Aliphatic polyarylates derived from L-n rosine A new class of biomaterials for biomedical applications. MSc Thesis, Rutgers University. ... 

Structures of symmetry Dn can be viewed as n-bladed propellers where, in a way, n screw fragments are grouped around a real or fictitious central unit. This category includes above all triaryl-element and comparable polyaryl-derivatives, doubly bridged biphenyls, and a number of twisted molecules. Here again the apparent helicities can easily be determined by evaluating the 4-point figures imprinted into the structural formulae. 

Noncrystalline aromatic polycarbonates (qv) and polyesters (polyarylates) and alloys of polycarbonate with other thermoplastics are considered elsewhere, as are aHphatic polyesters derived from natural or biological sources such as poly(3-hydroxybutyrate), poly(glycoHde), or poly(lactide) these, too, are separately covered (see Polymers, environmentally degradable Sutures). Thermoplastic elastomers derived from poly(ester—ether) block copolymers such as PBT/PTMEG-T [82662-36-0] and known by commercial names such as Hytrel and Riteflex are included here in the section on poly(butylene terephthalate). Specific polymers are dealt with largely in order of volume, which puts PET first by virtue of its enormous market volume in bottie resin. 

Polyarylates (PAr) are wholly aromatic polyesters derived from aromatic dicarboxylic acids and diphenols or their derivatives. They are amorphous in nature with good injection moldability. Figure 7 shows the typical formula structure of PAr. 

To the range of engineering plastics were added polyethylene and polybutylene tereph-thalates (PET and PBT), as well as General Electric s polyethers, the PPO (polyphenylene oxide) produced through polymerization of 2,6-xylenol and the Noryl plastic produced by blending PPO with polystyrene. Other special polymers, derived like the polycarbonates from bisphenol A, were added to this range polyarylates, polysul-fones, polyetherimides. 

A whole series of high-performance polyester LCPs was introduced in 1985. They were assembled from p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. Polyarylates (PARs) - amorphous phenolic esters derived from aromatic dicarboxylic acids (mixtures of terephthalic acid and isophthalic acid) and biphenols such as bisphenol A - are produced by Amoco (Ardel ), Celanese (Durel ) and DuPont (Arylon ) at a volume of approx. 2000 t/a. 

Fluorine-promoted stepwise polymerization of 4-fluorophenol derivative (23) provides a polyaryl ether (26) [7] where the fluorine atom plays an essential role in the activation of the reactive site in the chain extension step (Scheme 2.4). 

Poly(ethylene oxide) (PEO) has been employed frequently as a water-soluble catalyst support [9]. Further water-soluble polymers investigated include other linear polymers such as poly(acrylic acid) [10], poly(N-alkylacrylamide)s [11], and copolymers of maleic anhydride and methylvinylether [12], as well as dendritic materials such as poly(ethyleneimin) [10a, c] or PEO derivatives of polyaryl ethers [13]. The term dendritic refers to a highly branched, tree-like structure and includes perfectly branched dendrimers as well as statistically branched, hyperbranched macromolecules. 

Hydrazine derivatives also open the ring of pyrylium salts (18) to form open-chain products (19) which undergo recyclization. The applicability of this method of synthesis is strictly limited as only polyaryl pyrylium salts react smoothly. Of possible hydrazine derivatives, only alkyl or aryl hydrazines were used.33-41... 

S.L. Bourke, J. Kohn, Polymers derived from the amino acid 1-tyrosine polycarbonates, polyarylates and copolymers with poly(ethylene glycol), Adv. Drug Deliv. Rev. 55 (2003) 447-466. 

Figure 2 Synthesis of tyrosine-derived polyarylates. DIPC, 1,3-diisopropylcarbodiimide DMAP, dimethylaminopyridine PTSA, p-toluenesulfonic acid.

Theoretically chemical reaction rate reduction for ortho-derivative diphenol can be easily explained by steric factors. Within the frameworks of fractal analysis it is supposed, that solvents change at polyarylates syrrthesis should result to interactions polymer-solvent change. In this case the value of macromolecu-lar coil fractal dimension is determined according to the Eq. (12). In its turn, Flory-Huggins interaction parameter can be determined according to the Eq. (10). 

---