Dibenzyl structure on the macromolecular chain. XII. Polyureas: structure-property relatonships

anu, Elena Scor; Nicolaescu, Ioan; Caraculacu, Adrian A.; Caraculacu, Georgeta

doi:10.1002/1097-0126(200008)49:8<881::aid-pi508>3.0.co;2-a

Cited by 8 publications

(8 citation statements)

References 13 publications

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“…On the other hand, the peculiar crystallization tendency of the dibenzyl structure (DBDI), its alignment and packing ability are well known. As earlier reported [28,31,32], the MDI molecule introduces a rigid moiety (Ph-CH 2 -Ph) into the hard segment, whereas the DBDI (Ph-CH 2 -CH 2 -Ph) moiety introduces a more flexible structure into the hard segment due to the possible rotational conformation. As a result, in NEW HETEROCYCLIC POLYURETHANE-UREAS 885 this later case, the macromolecules can adopt more compact packing, mostly in the hard segments of polyurethanes.…”

Section: Thermal Propertiesmentioning

confidence: 55%

New Heterocyclic Polyurethane-ureas Based on 4,4'-dibenzyl diisocyanate. 2. Influence of Pyridine Units on the Mechanical Properties

Scortanu¹,

Prisăcariu²,

Hitruc³

et al. 2006

High Performance Polymers

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Heterocyclic polyurethane-ureas containing pyridine units on the main chain have been prepared by a two-step polyadition reaction. First, an urethane prepolymer was prepared in bulk starting from a macrodiol, which was a polyester-diol such as poly(ethylene adipate) (PEA) or a polyether-diol such as poly(tetramethylene glycol) (PTMG), and a diisocyanate such as 4,4 1 -dibenzyl diisocyanate (DBDI) or 4,4 1 -methylene-bis(phenyl-isocyanate) (MDI). The resulting urethane prepolymer containing NCO end groups was polymerized afterwards in DMF solution by using 2,6-diamino pyridine (DAPy) as chain extender, leading to polyurethane-ureas containing pyridine units The hard segments contents varied between 1.458-1.967 mol NHCOO/1000 g polymer. The resulting polymers were characterized by IR spectra, elemental and thermogravimetric analyses, differential scanning calorimetry, gel permeation chromatography, inherent viscosity, water retention measurements and mechanical properties. The study of the relationship between structure and properties reveals the influence of the nature of starting materials, macrodiols, the heterocyclic diamine and diisocyanates on the mechanical properties of the polymers. The large number of hydrogen bondings that formed between urea and urethane groups and the presence of pyridine rings in the polymer chain induced an improved thermal stability and good mechanical properties. The influence of the hard segment length was also studied. A greater length of the hard segments led to higher values of some mechanical tests such as: 100 and 300% moduli, strength stress and elongation at break. The mechanical behavior of these polymers is discussed and compared with that of earlier reported linear polyurethane-ureas based on MDI or with that of related polyurethanes chain-extended with diols.

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Section: Thermal Propertiesmentioning

confidence: 55%

New Heterocyclic Polyurethane-ureas Based on 4,4'-dibenzyl diisocyanate. 2. Influence of Pyridine Units on the Mechanical Properties

Scortanu¹,

Prisăcariu²,

Hitruc³

et al. 2006

High Performance Polymers

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“…It is known that the dibenzyl radicals favor the ordering in crystalline structure, leading for example in the case of polyureas, to crystallinity degrees of up to 67%. As earlier reported, the homopolyurea obtained from DBDI presented a crystallinity degree of 49.7% while the polyurea containing alternated structures of dibenzyl and diphenyl methane presented a higher crystallinity degree, namely 52.07% [8]. In polymer was synthesized which contained the diphenyl methane structure only, which is well known for reducing the polyurethane crystallinity.…”

Section: Wide-angle X-ray Scattering Measurementsmentioning

confidence: 68%

“…The effects of DBDI on polyurethane properties are quite important. As reported earlier [2,3,[6][7][8], the MDI molecule introduces a rigid moiety (Ph-CH 2 -Ph) in the hard segment, while the DBDI specific moiety (Ph-CH 2 -CH 2 -Ph) induces into the hard segment the possibility of an internal rotation of aromatic rings around the ethylene bridge. This leads to the appearance of both "syn" and "anti" rotational conformations, which coexist in the PU macromolecules based on DBDI.…”

Section: Introductionmentioning

confidence: 72%

“…The explaination of this behavior is the symmetry of aromatic diamines DAPO and DAB as well as of the DBDI which facilitates a higher hard-hard segment interaction. As discussed in the Introduction, the known tendency of dibenzyl structure (DBDI and DAB) to crystallize can lead to polymer precipitation [8]. On the other hand, the heterocyclic diamine has a symmetrical stiff molecule and thus the longer hard segments of PUU 4 contain a larger number of para substituted aromatic rings.…”

Section: Polymer Synthesismentioning

confidence: 99%

“…This leads to the appearance of both "syn" and "anti" rotational conformations, which coexist in the PU macromolecules based on DBDI. As a result, the macromolecules can adopt a more compact paking (in the case of the "anti" conformation), which increases the ordering tendency into crystalline structures [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

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New Heterocyclic Polyurethane-ureas based on 4,4′-dibenzyl diisocyanate, Part 1: Influence of Oxadiazole Structure on Mechanical Properties

Scortanu¹,

Prisăcariu²,

Caraculacu³

et al. 2006

High Performance Polymers

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A series of polyurethane-ureas was synthesized by solution polyaddition reaction of the following components: a polyester-diol, such as poly(ethylene adipate) (PEA), a polyetherdiol, such as poly(tetramethylene glycol) (PTMG) and a diisocyanate, such as 4,4′-dibenzyl diisocyanate (DBDI) or 4,4′-methylene-bis(phenyl-isocyanate) (MDI). In addition, 2,5-bis-(4-amino-phenylene)-1,3,4-oxadiazole (DAPO) was used as a chain extender. The hard segment content ranges between 1.384 and 1.819 mol NHCOO/1000 g polymer. For comparative studies, similar polyurethane-ureas were prepared by the same way but using 4,4′-methylene dianiline (MDA) and 4,4′-diamino-dibenzyl (DAB) as chain extenders. The resulting linear polymers were characterized by IR spectra, elemental and thermogravimetric analyses, differential scanning calorimetry, gel permeation chromatography, inherent viscosity measurements, wideangle X-ray scattering and mechanical properties. The study of the relationships between structure and properties reveals the influence of the nature of starting materials, macrodiols, the heterocyclic diamine and diisocyanates on the mechanical properties of the polymers. The great number of hydrogen bonding that formed between urea and urethane groups and the presence of oxadiazole rings in the polymer chain induced an improved thermal stability and good mechanical properties. The mechanical behavior of these polymers was discussed and compared with that of earlier reported linear polyurethane-ureas based on MDI or with that of related polyurethanes chain-extended with diols.

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Design, syntheses, and characterization of new thermoplastic polyureas based on 3,4‐ethylenedioxythiophene

Ojha

Ramesh

Kumar

2005

J. Polym. Sci. A Polym. Chem.

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New thermoplastic polyureas labeled PUn (n = 2, 3, 4, 6, 7, 9, or 10), based on 3,4‐ethylenedioxythiophene (EDOT) with flexible aliphatic spacers, were synthesized and characterized for the first time. EDOT was chosen as a replacement for the aromatic phenyl group in conventional thermoplastics based on urea linkages to improve solubility without compromising the thermal properties. As synthesized, all the samples exhibited a semicrystalline nature. The glass‐transition and melting temperatures showed a strong dependence on the spacer length. A comparison of the thermal properties of these polyureas with the corresponding phenyl analogues indicated that EDOT was a viable heteroatomic analogue of the phenyl group to be inserted into the main‐chain polyureas without hampering their thermal stability. The polyureas with spacer lengths greater than hexamethylene formed transparent gels in N‐methylpyrrolidone, 1,1,2,2‐tetrachloroethane, and dimethyl sulfoxide. The molecular packing of the polyureas was assigned with wide‐angle X‐ray diffraction studies. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5823–5830, 2005

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Dibenzyl structure on the macromolecular chain. XII. Polyureas: structure-property relatonships

Cited by 8 publications

References 13 publications

New Heterocyclic Polyurethane-ureas Based on 4,4'-dibenzyl diisocyanate. 2. Influence of Pyridine Units on the Mechanical Properties

New Heterocyclic Polyurethane-ureas Based on 4,4'-dibenzyl diisocyanate. 2. Influence of Pyridine Units on the Mechanical Properties

New Heterocyclic Polyurethane-ureas based on 4,4′-dibenzyl diisocyanate, Part 1: Influence of Oxadiazole Structure on Mechanical Properties

Design, syntheses, and characterization of new thermoplastic polyureas based on 3,4‐ethylenedioxythiophene

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