Comparative Study of the Conformational Characteristics of Partially Fluorinated Polyesters and Their Hydrogenated Counterparts

Reis-Nunes, R. C.; Riande, Evaristo; Chavez, N. C.; Guzmán, Julio

doi:10.1021/ma960405x

Cited by 6 publications

(7 citation statements)

References 25 publications

(75 reference statements)

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“…This behavior arises from differences in the modulus and orientation of the dipoles rather than from differences in the rotational populations about their respective skeletal bonds. The comparative analysis of the dipole autocorrelation coefficients of poly(neopentylglycol hexafluoroglutarate) (PNGHFG) and poly(neopentyl glycol glutarate) (PNG) confirmed these results . In this work, these studies are extended to the experimental and theoretical determination of the optical configuration parameter, Δ a , of PNGHFG networks.…”

Section: Introductionsupporting

confidence: 67%

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Stress Optical Behavior of Partially Fluorinated Aliphatic Polyesters

et al. 2000

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Thermoelastic networks were prepared by end-linking hdroxyl-terminated poly(neopentylglycol hexafluoroglutarate) using tris(p-isocyanate phenyl) thiophosphate as cross-linking agent. The plot of birefringence versus stress exhibits negative deviations from linearity at elongation ratios larger than 1.9. The value of the optical configuration parameter Δa is 2.98 Å3 at 5 °C. Theoretical calculations carried out using the rotational isomeric state model give for this parameter the value of 2.24 Å3, in fair agreement with the experimental results. The cause of the strong discrepancies between the theoretical and experimental results observed for the optical configuration parameter of polyesters containing phenyl groups in the acid residue is discussed.

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Section: Introductionsupporting

confidence: 67%

“…The conformational energies used were taken from the analysis of the dipole moments of diethyl hexafluoroglutarate 4 and poly(neopentyl glycol hexafluoroglutarate) . Gauche states about CF 2 −C*(O*) bonds of the acid residue have an energy E σα ca.…”

Section: Theoretical Calculations and Discussionmentioning

confidence: 99%

Stress Optical Behavior of Partially Fluorinated Aliphatic Polyesters

et al. 2000

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“…The inclusion of fluorine groups into polymers, more specifically, polyesters (1−4), has enabled the synthesis of materials with improved chemical resistance, low water absorption, low coefficients of friction, and low surface energies. In addition, fluorinated hydroxyl‐terminated polyesters have been used as polyurethane prepolymers (5), and it has also been found that the surface properties of fluorinated polyesters make them attractive for use as biomaterials (4).…”

Section: Introductionmentioning

confidence: 99%

Biocatalytic Synthesis of Fluorinated Polyesters

Mesiano

Beckman

Russell

2000

Biotechnology Progress

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The biocatalytic synthesis of fluorinated polyesters from activated diesters and fluorinated diols has been investigated. The effects of time, continuous enzyme addition, enzyme concentration, and diol chain length were studied to determine the factors that would limit chain extension, such as enzyme inactivation, enzyme specificity, the equilibrium position for the reaction, hydrolytic side reactions, and polymer precipitation. An enzyme screen demonstrated that only Novozym 435, an immobilized lipase from Candida antarctica, was effective in producing the fluorinated polyester. Molecular weight and polydispersity analyses were performed by means of gel permeation chromatography. End group analysis was accomplished through the use of matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy. Polymer molecular weight steadily increased and then leveled off after approximately 30 h, with a weight average molecular weight of approximately 1773. The majority of the polymer chains were terminated with either hydroxyl or vinyl groups. Polymers that were synthesized from bulk monomers had higher molecular weights, but high enzyme concentrations were required. Enzyme specificity toward shorter chain fluorinated diols appeared to be the governing factor in limiting chain growth. However, polymer molecular weight increased further (M(w) = 8094) when a fluorinated diol that contained an additional methylene spacer between the fluorine atoms and hydroxyl groups was used.

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“…A schematic representation of the repeating units of PNGHFG and PDET in their respective all‐ trans conformations are shown in Figs 1 and 2, respectively. Skeletal bond lengths, bond angles and the conformational energies associated with the rotational states were taken from the critical analysis of the dipole moments of diethyl hexafluoroglutarate7 and poly(neopentyl glycol hexafluoroglutarate)8 and the dipole moments and temperature coefficient of the unperturbed dimensions of poly(diethylene glycol terephthalate) 9. 10…”

Section: Theoretical Calculations and Discussionmentioning

confidence: 99%

“…The following main set of statistical weights was used 7. 8 E

_{σ_{α}}

= −0.5 kcal mol −1 , E

_{σ_{β}}

= 0.7 kcal mol −1 , E σ′ = −0.6 kcal mol −1 , E ω = E ω′ = E ω″ = 1.2 kcal mol −1 . The large soluble fraction of the networks precludes the possibility of knowing the average molecular weight between crosslinking points.…”

Section: Theoretical Calculations and Discussionmentioning

confidence: 99%

Stress–optical behaviour of polyester networks

Riande

Guzmán

2002

Polymer International

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Thermoelastic networks were prepared by end‐linking hydroxyl terminated chains of poly(neopentylglycol hexafluoroglutarate) (PNGHFG) and poly(diethylene glycol terephthalate) (PDET) using, respectively, tri(p‐isocyanate‐phenyl)‐thiophosphate and 2,4‐bis(p‐isocyanate benzyl)‐p‐phenylisocyanate as crosslinking agents. The plots of birefringence versus stress for PNGHFG and PDET networks exhibit negative deviations from linearity at elongation ratios greater than 1.9 and 5, respectively. The values of the optical configuration parameter Δa for the former and latter networks are 2.98 Å3 at 5 °C and 20.80 Å3 at 30 °C, respectively. Theoretical calculations carried out using the conformational energies obtained from the critical analysis of the mean‐square dipole moments of diethyl hexafluoroglutarate and poly(neopentylglycol hexafluoroglutarate) give the value of 2.24 Å3 at 5 °C for this parameter, in fair agreement with the experimental result. Similar calculations carried out on PDET networks give Δa = 3.74 Å3 at 30 °C, a value significantly lower than the experimental result. The cause of the strong discrepancy between the theoretical and experimental results observed for the optical configuration parameter of PDET is discussed. © 2002 Society of Chemical Industry

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Comparative Study of the Conformational Characteristics of Partially Fluorinated Polyesters and Their Hydrogenated Counterparts

Cited by 6 publications

References 25 publications

Stress Optical Behavior of Partially Fluorinated Aliphatic Polyesters

Stress Optical Behavior of Partially Fluorinated Aliphatic Polyesters

Biocatalytic Synthesis of Fluorinated Polyesters

Stress–optical behaviour of polyester networks

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