Block crystallization effect on the conformation of triblock oligomers α-n-alkyl-ω-n-alkoxyoligo(oxyethylene)s in the solid state

Fukuhara, Koichi; Hashiwata, K; Takayama, Kazuya

doi:10.1016/s0022-2860(99)00393-2

Cited by 6 publications

(31 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For short-chain symmetric C n E m C n triblocks (n ¼ 3-8, 10 and m ¼ 1-8) [10][11][12][13] and asymmetric triblocks H(CH 2 ) n (OCH 2 CH 2 ) m O(CH 2 ) n 0 H (C n E m C n 0 ) (n ¼ 8, n 0 ¼ 2-7 and m ¼ 4), 14 we have obtained the following results: both the alkyl and oligo(oxyethylene) blocks are crystalline, a highly extended alltrans planar form and a planar/helical/planar form exist, and the chain-length-dependent conformational transformation and polymorphism occur. The same experimental results have been reported by Rabolt and co-workers.…”

Section: Introductionmentioning

confidence: 99%

“…This latter form is subclassified into two, the b-form and the ab-form. [10][11][12][13][14] The difference between the two forms lies in the conformation around the CC-CO bonds on both sides of the central oligo(oxyethylene) block; the b-form assumes the gauche conformation around two of these bonds, while the ab-form assumes the trans conformation around one of them and the gauche conformation around the other. It has also been shown that the alkyl block of some of symmetric C n E m C n with n t m is partially crystalline or noncrystalline and contains conformational defects such as end-gauche and kink, while the oligo(oxyethylene) block is crystalline with normal helical conformation.…”

Section: Introductionmentioning

confidence: 99%

“…It has also been shown that the alkyl block of some of symmetric C n E m C n with n t m is partially crystalline or noncrystalline and contains conformational defects such as end-gauche and kink, while the oligo(oxyethylene) block is crystalline with normal helical conformation. 13 The chain-length-dependent conformational transformation of C n E m C n from the all-trans planar form into the planar/ helical/planar form or the transformation vice versa has been attributed to a crystallization competition between the oligo(oxyethylene) and alkyl blocks, and the unusual planar structure of the oligo(oxyethylene) block has been interpreted as a result from the conformational adaptation of this block to the restricted lattice space formed by the alkyl blocks. 13 Our recent thermal and infrared spectroscopic study on C 6 E m C 6 (m ¼ 1-7) with high purity (499.7%) has shown the relationship between the molecular conformation and the thermal behaviour, which depend on the number of oxyethylene units.…”

Section: Introductionmentioning

confidence: 99%

“…13 The chain-length-dependent conformational transformation of C n E m C n from the all-trans planar form into the planar/ helical/planar form or the transformation vice versa has been attributed to a crystallization competition between the oligo(oxyethylene) and alkyl blocks, and the unusual planar structure of the oligo(oxyethylene) block has been interpreted as a result from the conformational adaptation of this block to the restricted lattice space formed by the alkyl blocks. 13 Our recent thermal and infrared spectroscopic study on C 6 E m C 6 (m ¼ 1-7) with high purity (499.7%) has shown the relationship between the molecular conformation and the thermal behaviour, which depend on the number of oxyethylene units. 16 The relevant results are as follows: (1) the melting points of the g-form C n E m C n are significantly lower than those of the corresponding n-alkanes despite the same molecular form; (2) the planar structure of the central oligo(oxyethylene) chain in the g-form is stabilized by the force of the magnitude that maintains the rotator phase of n-alkanes; (3) the melting points of the g-form C 6 E m C 6 exhibit the odd-even alternation with respect to the number of oxyethylene units (m); (4) the bform C 6 E m C 6 melt via a partially melted phase where the alkyl blocks are melted; and (5) conformational polymorphism takes place for C 6 E 5 C 6 depending on solidification conditions.…”

Section: Introductionmentioning

confidence: 99%

“…This purity is much higher than the purity (95-99%) of the same compounds used for the previous studies. 11,13 2. Experimental 2.1.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Chain-length-dependent conformational transformation and melting behaviour of alkyl/oligo(oxyethylene)/alkyl triblock compounds: α-octyl-ω-octyloxyoligo(oxyethylene)s

Fukuhara

Mizawa

Inoue

et al. 2005

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

The chain-length-dependent conformational transformation and the melting behaviour of triblock compounds alpha-octyl-omega-octyloxyoligo(oxyethylene)s, H(CH2)8(OCH2CH2)mO(CH2)8H (abbreviated as C8EmC8) (m = 1-8), have been studied by infrared spectroscopy and differential scanning calorimetry. The compounds with m = 1-5 assume the all-trans planar form (gamma-form) in the solid state, while those with m = 7 and 8 assume the planar/ helical/planar form with conformational defects in the alkyl chain (beta'-form). Conformational polymorphism was observed for C8E6C8: the gamma-form for the annealed solid and the planar/helical/planar form without conformational defects (beta-form) for the unannealed solid. The conformational transformation from the planar form into the planar/helical/planar form takes place at a length of the oligo(oxyethylene) chain m = 6. This result for C8EmC8 and a similar conformational transformation for C6EmC6 at m = 5 (previous work) demonstrate that the conformation of the CnEmCn triblock compounds in the solid state is determined by intramolecular conformational restoring force in the central oligo(oxyethylene) block, intermolecular dipole-dipole interaction of the C-O bonds and intermolecular packing force in the end alkyl blocks. The melting points of the gamma-form solid of C8EmC8 are much lower than the melting points of n-alkanes with similar molecular masses. The observed thermodynamic quantities show that the planar structure of the oligo(oxyethylene) chain is stabilized by the force of the magnitude that maintains the rotator phase of n-alkanes. For the beta'-form solid of C8EmC8, the alkyl blocks, which are partially noncrystalline, and the oligo(oxyethylene) block melt together at the melting point, unlike the beta-form solid of C6EmC6, for which the melting of the alkyl blocks takes place before the melting of the oligo(oxyethylene) block. The beta-form solid of C8E6C8 (unannealed) melts via the gamma-form solid.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…This purity is much higher than the purity (95-99%) of the same compounds used for the previous studies. 11,13 2. Experimental 2.1.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Chain-length-dependent conformational transformation and melting behaviour of alkyl/oligo(oxyethylene)/alkyl triblock compounds: α-octyl-ω-octyloxyoligo(oxyethylene)s

Fukuhara

Mizawa

Inoue

et al. 2005

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

show abstract

Chain-Length-Dependent Conformational Transformation and Melting Behavior of Alkyl/Oligo(oxyethylene)/Alkyl Triblock Compounds: α-Hexyl-ω-hexyloxyoligo(oxyethylene)s

Fukuhara¹,

Mizawa²,

Inoue³

et al. 2003

J. Phys. Chem. B

View full text Add to dashboard Cite

The chain-length-dependent conformational transformation and melting behavior of triblock compounds α-hexyl-ω-hexyloxyoligo(oxyethylene)s, H(CH2)6(OCH2CH2) m O(CH2)6H (abbreviated as C6E m C6s) (m = 1−7), have been studied by differential scanning calorimetry and infrared spectroscopy. With an increase in the number of oxyethylene units (m), the molecular form of the triblock compounds in the solid state changes from an all-trans planar form (γ form) to a planar/helical/planar triblock form (β form) at m = 5. The melting points of the γ form C6E m C6s are much lower than the melting points of n-alkanes with similar molecular masses. This result is interpreted as due to the higher Gibbs energy of crystal for C6E m C6s. The observed thermodynamic quantities indicate that the planar structure of the oligo(oxyethylene) chain is stabilized by the force of the magnitude that maintains the rotator phase of n-alkanes. The β-form C6E m C6s melt stepwise through a solid−solid transition, at which the melting of only the alkyl blocks of the molecule occurs. The alkyl chains in the β-form C6E m C6s are loosely packed in the crystal even below the solid−solid transition temperature, while the crystallinity of the oligo(oxyethylene) block is significantly high. The molecular form of the alkyl/oligo(oxyethylene)/alkyl triblock compounds in the solid state is determined by the balance of the intramolecular conformational restoring force in the central oligo(oxyethylene) block and the intermolecular packing force in the end alkyl blocks. The conformational restoring force results from a tendency of the oligo(oxyethylene) chain to resume its intrinsic helical structure.

show abstract

Molecular Conformation and Melting Behavior of Alkyl/Oligo(oxyethylene)/Alkyl Triblock Position Isomers: Effect of the Position of an Oligo(oxyethylene) Block

Fukuhara

Kumamoto

2006

J. Phys. Chem. B

View full text Add to dashboard Cite

The molecular conformation and melting behavior of triblock position isomers H(CH(2))(k)(OCH(2)CH(2))(4)O(CH(2))(12)(-)(k)H (abbreviated as C(k)E(4)C(12)(-)(k)) with k = 6-11 have been studied by infrared spectroscopy and differential scanning calorimetry (DSC), with focus on the effect of the position of an oligo(oxyethylene) block in the molecule. The analysis of infrared spectra has revealed that the stable molecular form changes from a fully planar structure (gamma form) to a planar/helical/planar structure (beta form) with a change of the position of the tetrakis(oxyethylene) block from the center to the end of the molecule. The DSC measurements have shown that the melting points of the gamma-form solid decrease and the melting points of the beta-form solid increase with a shift of the tetrakis(oxyethylene) block toward the terminal of the molecule. The stabilities of the two molecular forms change over between k = 8 and 9. C(8)E(4)C(4) and C(9)E(4)C(3) exhibit contrasting conformational behavior with temperature; when the temperature is increased, the metastable beta form of C(8)E(4)C(4) transforms into the stable gamma form, while the metastable gamma form of C(9)E(4)C(3) transforms into the stable beta form. The metastable gamma form with a planar oligo(oxyethylene) block is a new finding in the present work. The experimental results of the stabilities of molecular forms are explained by the relative stabilities of partial crystal lattices formed by the alkyl and oligo(oxyethylene) blocks.

show abstract

Block crystallization effect on the conformation of triblock oligomers α-n-alkyl-ω-n-alkoxyoligo(oxyethylene)s in the solid state

Cited by 6 publications

References 18 publications

Chain-length-dependent conformational transformation and melting behaviour of alkyl/oligo(oxyethylene)/alkyl triblock compounds: α-octyl-ω-octyloxyoligo(oxyethylene)s

Chain-length-dependent conformational transformation and melting behaviour of alkyl/oligo(oxyethylene)/alkyl triblock compounds: α-octyl-ω-octyloxyoligo(oxyethylene)s

Chain-Length-Dependent Conformational Transformation and Melting Behavior of Alkyl/Oligo(oxyethylene)/Alkyl Triblock Compounds: α-Hexyl-ω-hexyloxyoligo(oxyethylene)s

Molecular Conformation and Melting Behavior of Alkyl/Oligo(oxyethylene)/Alkyl Triblock Position Isomers: Effect of the Position of an Oligo(oxyethylene) Block

Contact Info

Product

Resources

About