Up-down disorder in the crystal structure of form III of isotactic poly(4-methyl-1-pentene)

Crystal Structure of Form II of Syndiotactic Poly(1-butene)

“…Various isotactic polymers, having chains in the fourfold helical s(4/1) conformation or in the complex helical s(M/N) conformation, with M and N not corresponding to very small integers or with fractional ratio M/N, are crystallized in a tetragonal lattice. Some examples are form I and form III of isotactic poly(4methyl-1-pentene) (7 2 helices and space group P4 h or P4 hb2 for the form I, 14-17 4 1 helices and space group I4 1 for the form III 18,19 ), form II of isotactic poly(1-butene) (11 3 helices and space group P4 h), 20,21 isotactic poly[(R),-(S)-4-methyl-1-hexene] (7 2 helices and space group P4 h), 16 form I of isotactic poly(vinylcyclohexane) (4 1 helices and space group I4 1 /a), 22,23 isotactic poly(o-methylstyrene) (4 1 helices and space group I4 1 cd), 24 and isotactic poly-(m-methylstyrene) (11 3 helices and space group P4 h). 25 Among syndiotactic polymers, only one example has been found so far, that is syndiotactic poly(4-methyl-1- pentene), characterized by s(12/7)2 helical chains packed in a tetragonal lattice with space group P4 h. 12 Exceptions to this simple rule have been found for form III of isotactic poly(1-butene), characterized by 4 1 helical chains packed in an orthorhombic lattice with space group P2 1 2 1 2 1 , 26 and for isotactic poly(3-methyl-1-butene), characterized by 4 1 helical chains packed in a monoclinic lattice with space group P2 1 /b.…”

Chain Conformation, Crystal Structures, and Structural Disorder in Stereoregular Polymers

“…33,153 The low symmetry of the packing comes from the fact that two of the four chains included in the tetragonal unit cell are independent, that is, are not related by d (ppm) The methyl carbon atoms of the two independent chains present, indeed, different crystallographic environments since the contact distances with the neighboring atoms are different. 152 The low-symmetry model describes the local arrangement of the chains, which can be detected only by direct observation of a very small area of the diffracting crystals.…”

Approach to nonisothermal crystallization kinetics of poly(4‐methyl‐1‐pentene) melt: Effect of gamma‐ray

“…Poly(4-methyl-1-pentene) (PMP), which consists of carbon and hydrogen atoms, is a thermoplastic polymer and has been widely used in gas-permeable packaging, medical and laboratory equipment. PMP has five different polymorphisms: Form I-crystalline phase with helical polymer chains of a 7 2 helix in tetragonal structure from melt, [1,2] Form II-crystalline phase with helical polymer chains of a 4 1 helix in monoclinic structure from tetramethyl-tin solution, [3] Form III-crystalline phase with 4 1 helical conformation in tetragonal structure from nheptane solutions, [4] and Forms IV and V-crystalline phases in hexagonal structure of a = 22.17 Å and c = 6.50 Å and 6.69 Å, respectively, from cyclopentane solutions. [5,6] The polymorphisms make PMP an ideal candidate to "react" with other materials to form polymer composites, such as PMP/clay nanocomposites, [7] PMP-carbon nanotubes [8] and antimicrobial polymers, [9] for a variety of applications, including automotive, [10] membrane, [11,12] energy storage, [6] and so on.…”