Dibenzyl Structures in Macromolecular Chains

Caraculacu, Adrian A.; Caraculacu, Georgeta

doi:10.1080/00222338508056627

Cited by 17 publications

(8 citation statements)

References 7 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: 82%

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: 82%

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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“…In a series of recent theoretical and experimental studies we have reported on a systematic investigation on the effect of varying hard and soft segment chemistry, crosslinking and preparation procedures. The structure and mechanical response of melt-cast and solution-cast PUs derived from classical conventional rigid di-118 C. PRISACARIU and E. SCORTANU isocyanates (DI), were compared with a new family of dibenzyl-containing PU derived from the flexible 4,4 1 -dibenzyl diisocyanate (DBDI) [2][3][4][5]. In our earlier studies we investigated the effect of the newly introduced spacer group/ethylene bridge (-CH 2 -CH 2 -) between the aromatic rings of DBDI, on the structure and properties of such polymers.…”

Section: Introductionmentioning

confidence: 99%

“…In our earlier studies we investigated the effect of the newly introduced spacer group/ethylene bridge (-CH 2 -CH 2 -) between the aromatic rings of DBDI, on the structure and properties of such polymers. We showed that the chain packing of the DBDI-based PUs was strikingly different than that for commercial PUs of similar structure based on the more commonly used 4,4 1 -methylene bis (phenyl isocyanate) MDI [1][2][3][4][5][6][7]. The ability of the two benzene rings to rotate in the two discrete "syn" and "anti" positions around the -CH 2 -CH 2 -ethylene bridge (figure 1) enables a specific coplanar packing structure of the hard domains.…”

Section: Introductionmentioning

confidence: 99%

Infrared Dichroic Studies of Phase Separation and Orientation of Dibenzyl Hard Segments in Polyurethane

Prisăcariu

Scortanu

2007

High Performance Polymers

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Polyurethanes (PUs) based on diethylene glycol (DEG) and a new isocyanate of variable geometry, 4,4'-dibenzyl diisocyanate (DBDI), were synthesized by the standard two-step procedure. A macro-diol, hydroxyl-terminated poly(ethylene adipate) (PEA) MW = 2000 50 (PEA2000 ) was also used in the PU synthesis. The ability of the two benzene rings in the DBDI unit to rotate in two discrete “sin” and “anti” positions around the —CH2CH2— ethylene bridge enables a specific coplanar packing structure of the hard domains dibenzyl-based polymers. Molecular orientation of the DBDI-based hard segments and soft segments was monitored by means of infrared dichroic experiments. The effect of the strain history on the orientation of macromolecular chains was studied under uniaxial extension and in cyclical deformation experiments. The high modulus domains derived from the DBDI unit containing the aromatic urethane blocks served to reinforce the rubbery prepolymer phase. Since the two (soft and hard) phases are interpenetrating, both were deformed by the applied stress. When the load was removed, the soft domains relaxed to a nearly isotropic state, while the rigid phase remained plastically deformed.

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“…A solution of mercaptobenzothiazole (MBT) was obtained by mixing 23 g (0.1373 mol) with 250 mL 1,2-dichloroethane (DCE) and 50 mL acetone, then heating gradually to 35-50°C for 0.5 h until the mixture became homogeneous. A solution of 1,2-bis(p-isocyanato-phenyl)ethane (4,4'-dibenzyl diisocyanate) [3,4] (17 g, 0.0644 mol) in 100 mL DCE was added to this mixture under stirring during 0.25 h and then 0.2 g diazabicyclo[2.2.2]octane (DABCO) also was added. The mixture was stirred at 68-72°C for 6 -8 h. After cooling, the light yellow solid was isolated by filtration, washed with DCE and acetone (to remove the excess of MBT) and dried at 90-100°C (22.5 g, 57.73% yield).…”

mentioning

confidence: 99%

1,2-Bis(p-phenyl-thiocarbamic Acid-S-benzothiazol-2-yl-ester)ethane and 1-(o-Phenyl-thiocarbamic Acid-S-benzothiazol-2-yl-ester)-2-(p-phenyl-thiocarbamic Acid-S-benzothiazol-2-yl-ester)ethane

Scortanu

Caraculacu

2003

Molbank

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The experimental procedure follows the general synthesis of blocked isocyanates [1,2]. A solution of mercaptobenzothiazole (MBT) was obtained by mixing 23 g (0.1373 mol) with 250 mL 1,2-dichloroethane (DCE) and 50 mL acetone, then heating gradually to 35-50°C for 0.5 h until the mixture became homogeneous. A solution of 1,2-bis(p-isocyanato-phenyl)ethane (4,4'-dibenzyl diisocyanate) [3,4] (17 g, 0.0644 mol) in 100 mL DCE was added to this mixture under stirring during 0.25 h and then 0.2 g diazabicyclo[2.2.2]octane (DABCO) also was added. The mixture was stirred at 68-72°C for 6 -8 h. After cooling, the light yellow solid was isolated by filtration, washed with DCE and acetone (to remove the excess of MBT) and dried at 90-100°C (22.5 g, 57.73% yield).The synthesis of the nonsymmetrical isomer is described as follows. To a solution of MBT (5 g, 0.029895 mol) in 100 mL DCE and 15 mL acetone, 1-(o-isocyanato-phenyl)-2-(p-isocyanato-phenyl)ethane (2,4'-dibenzyl diisocyanate) (3.42 mL, 3.8 g, 0.01439 mol) and 0.1 g DABCO was added. The mixture was stirred for 10 h at 70-72°C. After cooling, the solid product was isolated by filtration, washed several times with acetone and dried (3 g, 34.84% yield).

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Dibenzyl Structures in Macromolecular Chains

Cited by 17 publications

References 7 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

Infrared Dichroic Studies of Phase Separation and Orientation of Dibenzyl Hard Segments in Polyurethane

1,2-Bis(p-phenyl-thiocarbamic Acid-S-benzothiazol-2-yl-ester)ethane and 1-(o-Phenyl-thiocarbamic Acid-S-benzothiazol-2-yl-ester)-2-(p-phenyl-thiocarbamic Acid-S-benzothiazol-2-yl-ester)ethane

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