Poly pivalolactone

60% of hard segments are also soluble in dichloromethane, chloroform and 1,1,1 -trichloroethane. 

In spite of their somewhat high price relative to most conventional rubbers these materials have become widely accepted as engineering rubbers in such applications as seals, belting, water hose and even low-pressure tyres. 

For an aliphatic polyester, poly(pivalolactone) has a rather high of 245°C and for such a an unexpectedly low of -10°C. It is also claimed to have good hydrolysis resistance for a polyester and this appears to be one of the reasons for its manufacture on an experimental scale by Shell with a view for use as both a fibre and as a thermoplastics moulding material. 

The polymer has a regular structure and is therefore crystallisable. Three crystalline forms are known  

A 100% crystalline material has a density of 1.223 g/cm at 20°C, a fully amorphous material a density of 1.097 g/cm whilst samples cooled normally in a mould have a value of 1.19 g/cm.  

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Poly(pivalolactone) 739 Table 25.12 Propenies of Hytrel-type thermoplastic elastomers... 

Liquid crystal polyesters Polyester Thermoplastic Elastomers Poly(pivalolactone)... 

Synthesis and Characterization of Poly (oxyethylene)-6-poly(pivalolactone)Telechelomer... 

Figure I indicates the approach used to synthesize poly(oxyethylene)-b-poly(pivalolactone) telechelomers. An acetal capped anionic initiator, X (13) polymerizes ethylene oxide (EO) to give 2> a potassium alkoxide of a masked polyether, and this "new" initiator is to be used to polymerize pivalolactone (PVL). Since potassium alkoxides are strong nucleophiles, they can randomly attack at both the carbonyl carbon and the 3-methylene carbon in lactones, (Figure 2) such a random attack would result in a pivalolactone segment containing irregularities. Lenz (15), and Hall (16), and Beaman (17) have investigated PVL polymerization and have shown that the less nucleophilic carboxylate anion is preferable in polymerizing PVL smoothly. The weaker carboxylate anion will attack only at the methylene...

Figure i. Synthetic scheme for poly(oxyethyIene)-b-poly(pivalolactone) telechelomer. 

Figure 3. Apparatus for the synthesis of poly(oxyethylene)-b-poly(pivalolactone) salt, k.

The possibility exists that the acid used in hydrolysis could catalyze the hydrolysis of the succinic ester group in the middle of the telechelomer itself. Even though NMR ( H and C) cannot easily eliminate this possibility, we have evidence that such a hydrolysis did not take place. For instance, hydrolysis should result in the formation of poly(pivalolactone) which is insoluble both in methylene chloride and water, but no insolubles were evident. Also, the Gel Permeation Chromatograms do not show impurities in the product. 

In the case of crystals, both intramolecular (conformational) and packing energies should be taken into account simultaneously. Such a total energy minimization method, with suitable crystallographic constraints, has been applied in different steps of the analysis of crystalline structures of three different synthetic polymers. Structures of these molecules, namely, isotactic trans-1,4-poly-penta-1,3-diene (ITPP), poly-pivalolactone (PPVL), and isotactic cis-1,4-poly(2-methyl-penta-1,3-diene)(PMPD), do not have troublesome features such as charged groups, counterions, and solvent molecules. 

Poly(PVL-b-IB-b-PVL) Poly(pivalolactone-Z Zock-isobutylene-Z Zock-pi valolactone) triblock copolymer... 

PpClaMeSt PPVL PVL PSt -St-IB-Cl triblock copolymer Poly(p-chloro-a-methylstyrene) Poly(pivalolactone) Pivalolactone Polystyrene Dormant polymer end with styrene as the penultimate and isobutylene as the ultimate monomer unit... 

Homogeneous nucleation is always primary. It occurs very rarely, and appears only to have been observed with melts of poly(pivalolactone) and poly(chlorotrifluoroethylene) when they are strongly undercooled. Since the nucleation is a spontaneous process, it must be sporadic, that is, nuclei form successively and an increase in number of spherulites with time is observed. Such effects are not only observed by homogeneous nucleation, however, but... 

As a consequence of the a to P transition which accompanies orientation, fibre patterns of the a-form are difficult to obtain. Melt extruded fibres of poly(a,a-dimethyl-P-propiolactone), known as poly(pivalolactone) (PPL), do, however, crystallize in the a-form and retain their orientation upon high temperature annealing under tension . Furthermore, oriented samples of poly(a-methyl-a-n-propyl-B-propiolactone) (PMPPL) have been prepared which show x-ray layer lines corresponding to the two phases. The a-form of both PPL and PMPPL is characterized by a fibre repeat distance of about 6 A, which has been identified as the periodicity of a 2j helix. Although oriented samples of poly(a-methyl-a-ethyl-B-propiolactone) (PMEPL) in the a-phase have never been reported, x-ray powder data have been fitted with a monoclinic unit cell with c = 6.1 A. 

Poly(pivalolactone) is the polyester of hydroxy pivalic acid. Pivalo-lactone is used as monomer since hydroxy pivalic acid does not polycondense to high molar masses. Living zwitterions are formed with tributyl phosphine as initiator and these add on further pivalolactone ... 

The crystal structure of poly(pivalolactone) has been investigated by methods similar to the above, where the internal structure is allowed to be optimized along with the crystal packing [26]. 

Blends of polycarbonates and polyester have been covered in Section 2, however, the properties of compatible blends of polycarbonate and a copolyester have been described. Polycarbonate blends with poly(pivalolactone) have been found to be completely immiscible. Steric hinderance has been offered as a possible explanation. - ... 

Various polyesters such as poly (butylene terephthalate) have also been shown to be compatible with bisphenol A phenoxy resin. The suggested specific interaction here is between the hydroxyl of the phenoxy resin and the ester carbonyl. A wide range of polyesters have, however, also been found to be compatible with polycarbonates," where no hydroxyl groups are present. One might therefore consider that some interaction with the aromatic ring should be invoked of the sort that has been presumed to exist in the compatible pair, polystyrene-poly(vinyl methyl ether). A notable exception to the compatibility exhibited above is poly(pivalolactone) where the methyl groups might sterically hinder the interactions."... 

Fig. 6.12 Plot of melting temperature against characteristic ratio for indicated polymers. (1) Polyethylene (2) i-poly(propylene) (3) i-poly(isopropyl acrylate) (4) s-poly(isopropyl acrylate) (5) i-poly(methyl methacrylate) (6) s-poly(methyl methacrylate) (7) poly(dimethyl siloxane) (8) poly(diethyl siloxane) (9) poly(dipropyl siloxane) (10) poly(cis-l,4-isoprene) (11) poly(trans-l,4-isoprene) (12) poly(cis-1,4-butadiene) (13) poly(trans-1,4-butadiene) (14) poly(caprolactone) (15) poly(propiolactone) (16) poly(pivalolactone) (17) poly(oxymethylene) (18) poly(ethylene oxide) (19) poly(trimethylene oxide) (20) poly(tetramethylene oxide) (21) poly(hexamethylene oxide) (22) poly(decamethylene oxide) (23) poly(hexamethylene adipamide) (24) poly(caprolaetam) (25) poly(ethylene terephthalate) (26) poly(ethylene sulfide) (27) poly(tetrafluoroethylene) (28) i-poly(styrene) (29) poly(acrylonitrile) (30) poly(l,3-dioxolane) (31) poly(l,3-dioxopane) (32) poly(l,3-dioxocane) (33) bisphenol A-poly(carbonate).

PE = polyethylene, PP = polypropylene, PES = poly (ethylenesulphide), PPVL = poly(pivalolactone). 

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