Poly 4-methyl pentene structure

The intramolecular interaction energy was calculated for five isotactic polymers, namely, isotactic polypropylene, poly(U-methyl-l-pentene), poly(3-methyl-1-butene), polyacetaldehyde, and poly(methyl methacrylate) (23). The molecular structures of the first four polymers have already been determined by x-ray analyses as (3/1) (2k), (7/2) (18,25.,26), (U/l) (21), and (U/l) helices (28), respectively. Here (7/2) means seven monomeric units turn twice in the fiber identity period. For isotactic poly(methyl methacrylate) (29), a (5/l) helix was considered reasonable at the time of the energy calculation in 1970, before the discovering of... 

Finally, we have attempted to evaluate the possible impact of an intermediate liquid crystalline phase and the possibility of transfer of helical hand information from the melt to the crystal throughout this process. Assuming that the melt is structured, the melt of chiral but racemic polyolefins would be made of stretches of helical stems that are equally partitioned between left- and right-handed helices. Formation of antichiral structures (such as in a iPP) could be interpreted as indicating a possible transfer of information (but the problem of the sequence of helical hands would still remain). This analysis is, however, ruined by the observation that many of these polymers also form chiral structures (frustrated p phase of iPP, Form III of iPBul). For the achiral poly(5-methyl-pentene-l), the chiral, frustrated phase is actually the more stable one, and can be obtained by melting and recrystallization of a less stable antichiral phase. 

A linear polymer is one in which each repealing unit is linked only to two others. Polystyrene (1-1), poly(methyl methacrylate) (1-34), and poly(4-methyl pentene-1) (1-35) are called linear polymers although they contain short branches which arc part of the monomer structure. By conirast, when vinyl acetate is polymerized by free-radical initiation, the polymer produced contains branches which were not present in the monomers. Some repeating units in these species are linked to three or four other monomer residues, and such polymers would therefore be classified as branched. 

The case of conformational isomorphism of lateral groups occurs, for instance, in the crystal structure of isotactic poly(S-3-methyl-pentene), characterized by the presence of fourfold helices of only one sense (left-handed), with lateral groups which may adopt statistically two conformations of minimum energy [99,103]. 

Other polymers with properties similar to those of picarin include a copolymer of norbornene and ethylene (NEC), which has a transmission of about 90% (for a 2 mm-thick sample) in the frequency range between 0.2 and 1.2THz [111], and poly(4-methyl pentene-1) (TPX Mitsui Chemicals). The latter is transparent at UV, visible and far-IR frequencies [112]. The chemical structures of the base units of these polymers are provided in Chart 2.13. 

In the crystal structures of many other isotactic polymers, with chains in threefold or fourfold helical conformations, disorder in the up/down positioning of the chains is present. Typical examples are isotactic polystyrene,34,179 isotactic poly(l-butene),35 and isotactic poly(4-methyl-l-pentene).39,40,153,247... 

Poly (4-methyl-1-pentene). Poly(4-methyl-l-pentene) has not yet drawn much attention in radiation chemistry. As far as we know, only one study on high energy-irradiated poly(4-methyl-l-pentene) has been published (25), and this was in the form of a short communication. The ESR spectrum at liquid nitrogen temperature was a sextet with a hyper-fine splitting constant of 23 gauss. The radicals producing this spectrum were supposed to have structure XXI—i.e., radicals formed by side-chain scission. 

The ESR spectrum of radicals in poly(4-methyl-l-pentene) induced by ultraviolet light 4,5) is composed of a sharp quartet with the hyper-fine splitting constant of 22.5 gauss and a broad quartet. The sharp component has been attributed to methyl radicals (XI) while the broad component could be caused by polymer radicals of structures XXIII and/or XXIV. 

The structure of a poly(4-methyl-l-pentene) (TPX) homopolymer is shown in Figure 4.1. Actually, TPX is a registered trademark from various companies, with a different meaning. Sometimes TPX is also abbreviated as PMP. 

In spite of the similarity of the structure of the monomer units the two corresponding isotactic polymers crystallize in two different chain conformations tiie helix of poly-3-methyl-l-butene contains four monomer units per turn (4/1) with a chain repeat of 6.85 A the helix of poly-4-methyl-l-pentene contains 3.5 units per turn (7/2) and has a repeat of 13.85 A. The copolymers tend to crystallize. Their chain conformation and cross sectional area in the crystal lattice are analogous to those of the homopolymer corresponding to the predominant comonomer. For 4-methyl-l-pentene contents higher than 50% some evidence exists that the system simultaneously contains both chain conformations. 

The first objective of this work was to explore by high resolution H NMR and 13CNMR spectroscopy the detailed structures of poly(3-methyl-l-butene) and poly(4-methyl-l-pentene) obtained by cationic isomerization polymerization. 

The results of the study of the effect of synthesis conditions on the composition of poly(4-methyl-l-pentene) have shown that even under conditions most favorable for the successful competition of isomerization with propagation, i.e., —120° C, using EtAlCl2, in ethyl chloride, the polymer contains only 50% of the desired 1,4-structure. It appears that in the series (n— l)-methyl-l-alkenes as n increases the likelihood of obtaining completely isomerized products via cationic isomerization polymerization is decreased. This is supported qualitatively by results obtained in the cationic polymerization of 4-methyl-l-hexene, an (n—2)-methyl-1-alkene (17). 

The 300 MHz H NMR and 20 MHz 13C NMR spectra of poly(4-methyl-l-pentene) have been found to be more complex than the corresponding spectra of poly(3-methyl-l-butene) due to the presence of an additional isomer structure in the polymer. Investigation of the 20 MHz 13C NMR spectrum of the polymer has indicated that placement of units in different triad sequences is die cause of multiple methyl proton resonances which have been observed in the H NMR spectra of poly(3-methyl-l-butene) and poly(4-methyl-l-pentene). The use of a computer program for simulating and plotting spectra has enabled measurements of polymer composition to be made of poly(4-methyl-l-pentene) s prepared under a variety of synthesis conditions. 

As shown in Table 22 in most examples, the prevailing absolute configuration of the asymmetric carbon atoms of the lateral chains of the first eluted fractions is opposite to the one of the support this indicates that the polymer having the same structure as the support is more strongly adsorbed. However, this is not a general phenomenon, as it is shown by the chromatography of poly-3.7-dimethyl-l-octene obtained from the racemic monomer using poly-(S)-3-methyl-l-pentene as support (118). 

When linear a-olefins are polymerised, the polymer contains only methyl branches, regularly distributed along the chain with a separation corresponding to the size of the alkyl substituent in the monomer. It may be interesting that the structure of the polymer formed from 1-pentene, poly[2,5-(l-... 

An example of a branched polymer used as a synthetic elastomer is poly(4-methyl-1-pentene), CAS 25068-26-2 [134]. The idealized structure of poly(4-methyl-1-pentene) and the formulas of a few molecular fragments found in the pyrolysate of this polymer are shown below ... 

---