Viscosity – Molecular Weight Relationships and Unperturbed Dimensions of Linear Chain Molecules

Kurata, Michio; Tsunashima, Yoshisuke

doi:10.1002/0471532053.bra049

Cited by 85 publications

(96 citation statements)

References 831 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Judging from this sensitivity of G e to the osmotic environment for the corona (determined by the solubility), we speculate that the moderate difference in the G e =k B T values for the PS-PI/C14 and PS-PB/C14 systems ( Figure 3) may reflect a slight difference of the solubilities of PI and PB blocks in C14. (As judged from a difference of the Mark-Houwink-Sakurada exponents in hexane/heptane chemically similar to C14, ¼ 0:58 for PI/hexane solutions 17 and ¼ 0:64 for PB/heptane 18 solutions (both values obtained from five fractions), C14 appears to be slightly poorer for PI than for PB thereby giving somewhat larger G e for PS-PI.) A further study is desirable for this delicate solvent effect.…”

Section: Structural Factors Determining Equilibrium Modulusmentioning

confidence: 94%

Further Investigation of Equilibrium Modulus of Diblock Copolymer Micellar Lattice

Tan

Watanabe

2004

Polym J

View full text Add to dashboard Cite

ABSTRACT:Polystyrene-polybutadiene (PS-SB) and polystyrene-polyisoprene (PS-PI) diblock copolymers form spherical micelles with PS cores and PB/PI corona in a PB/PI-selective solvent, n-tetradecae (C14). At high concentrations, the micelles are further arranged on bcc lattices. Structural factors governing the equilibrium modulus G e of these PS-PB and PS-PI micellar lattices are discussed in this study. It turned out that G e is primarily determined by the number density of the corona blocks corona and proportional to corona while the number density of the bcc lattice cell, D À3 with D being the lattice spacing (determined from SAXS), has only secondary effects on G e . The proportionality between G e and corona reflects the thermodynamic origin of the lattice elasticity, the entropic elasticity of the corona PB/PI blocks having osmotically correlated conformations. These results suggest a necessity of re-examination of a previous hypothesis that the cell number density primarily determines G e of bulk copolymer systems forming cubic phases [Kossuth et al., J. Rheol., 43, 167 (1999)]. Furthermore, the G e = corona ratio was found to be moderately different for the PS-PB/C14 and PS-PI/C14 micellar lattices. This difference can be related to a difference in the magnitude of the osmotic correlation for the PB and PI corona blocks due to a slight difference of their solubilities in C14. [DOI 10.1295/polymj.36.430] KEY WORDS Diblock Copolymer Micellar Lattice / Equilibrium Modulus / Osmotic Requirement / Lattice Stability / Diblock copolymers form micelles with precipitated cores and solvated corona in selective solvents. These micelles form cubic lattices at high concentrations where the corona blocks of neighboring micelles are overlapping each other. [1][2][3][4][5][6] This lattice formation results from a compromise of contradicting thermodynamic requirements, an elastic requirement of randomizing corona conformation and an osmotic requirement of reducing the spatial gradient of the corona concentration.1,4-6 Under these requirements, the corona blocks of neighboring micelles are forced to have mutually correlated conformations. The micelles are arranged on cubic lattices so as to satisfy the thermodynamic requirements and minimize this correlation.The micellar lattice is the thermodynamically stable structure and exhibits equilibrium elasticity.1-6 For polystyrene-polybutadiene (PS-PB) copolymers in a PB-selective solvent, n-tetradecane (C14), the equilibrium modulus G e was found to be proportional to the number density corona of the corona PB blocks and the proportionality constant (G e = corona ratio) was smaller than the constant k B T expected for the simplest case of the entropic elasticity of independent corona blocks (k B = Boltzmann constant and T = absolute temperature). [4][5][6] This proportionality reflects the thermodynamic origin of the lattice. Namely, the osmotically correlated corona blocks sustain the lattice and thus their number density is the primary factor determining G e . At the same ...

show abstract

Section: Structural Factors Determining Equilibrium Modulusmentioning

confidence: 94%

Further Investigation of Equilibrium Modulus of Diblock Copolymer Micellar Lattice

Tan

Watanabe

2004

Polym J

View full text Add to dashboard Cite

show abstract

“…Considerando-se a lei de Poiseuille [25,26] para escoamento laminar em tubos capilares é possível determinar a viscosidade da solução. Realizando-se uma série de simplificações e considerações que são descritas na literatura [13,24] , chega-se à uma expressão que relaciona as diferenças de pressão no viscosímetro com a viscosidade específica: tornou essa técnica atrativa para a determinação de massas molares absolutas e outras propriedades de polímeros em solução [12][13][14] . Através de medidas viscosimétricas on-line em conjunto com GPC, Ouano [15] obteve bons ajustes para a equação de Mark-Houwink-Sakurada (MHS).…”

Section: Cromatografia De Permeação Em Gel (Gpc)unclassified

“…Os filmes foram secos em estufa a vácuo a 40 °C por 48 horas para remoção total do solvente. [13,14,25,27,28] :…”

Section: Determinação Do Grau De Conversão Da Reação Do Ps-possunclassified

“…A constante α está relacionada com o tipo de conformação da cadeia polimérica em solução. Na condição não perturbada teta (θ), um polímero com cadeias lineares e flexíveis apresenta α igual a 0,5 [14,29,30] . Quando há uma boa interação entre polímero e solvente, um polímero com cadeias lineares e flexíveis apresenta α entre 0,5 e 0,8.…”

Section: Determinação Do Grau De Conversão Da Reação Do Ps-possunclassified

See 1 more Smart Citation

Caracterização viscosimétrica de nanocompósitos híbridos PS/POSS

et al. 2012

View full text Add to dashboard Cite

Resumo: Nanocompósitos híbridos de poliestireno (PS) e poliedros oligoméricos silsesquioxanos (POSS) com diferentes composições e graus de hibridização foram obtidos por processamento reativo no estado fundido utilizando-se peróxido de dicumila (DCP) como iniciador, na presença ou não de estireno como agente de transferência de radical. Os materiais foram caracterizados viscosimetricamente por cromatografia de permeação em gel (GPC) usando detecção tripla por espalhamento de luz, viscosimetria e índice de refração. As amostras PS/POSS processadas com estireno apresentaram maiores valores de massa molar ponderal média (M w ) e menores valores de polidispersão (M w /M n ), devido ao maior grau de conversão da reação de hibridização do PS-POSS (28-40%) e do menor grau de degradação (cisão) das cadeias do PS, quando comparadas com amostras PS/POSS processadas sem estireno nas quais o grau de conversão ficou em torno de 24-28%. Para os sistemas PS e PS/POSS em solução com THF, os parâmetros da equação de Mark-Houwink-Sakurada (MHS), α ≅ 0,7 e log K ≅ -3,5 a -3,9 e os valores dos parâmetros de interação polímero-solvente, χ ij ≅ 0,49, não apresentaram diferenças significativas com relação aos tamanhos moleculares. Por outro lado, essas diferenças de tamanhos moleculares foram caracterizadas por uma função cumulativa da fração mássica de cadeias em função da distância média quadrática entre pontas de cadeia ( ) Palavras-chave: PS, POSS, nanocompósitos híbridos, viscosimetria. Viscometric Characterization of PS/POSS Hybrid NanocompositesAbstract: Polystyrene (PS) and polyhedral oligomeric silsesquioxanes (POSS) hybrid nanocomposites with different compositions were obtained by reactive melt processing using dicumyl peroxide (DCP) as initiator in the presence or absence of styrene as radical transfer agent. The materials were characterized by viscosimetry by means of gel permeation chromatography (GPC) using triple-detector: light scattering, viscometer and refractive index. PS/POSS samples processed with styrene showed higher weight average molecular weights (M w ) and lower polydispersity indexes (M w /M n ), as a result of higher PS-POSS conversion (28-40%) and lower PS degradation, as compared to the PS/POSS samples processed without styrene in which the degree of conversion was lower (24-28%). For the PS/POSS solutions in THF, the parameters of the Mark-Houwink-Sakurada equation, α ≅ 0.7 and log K ≅ -3.5 to -3.9, and the values of polymer-solvent interaction parameter, χ ij ≅ 0.49, were not changed with respect to changes in molecular size. On the other hand, these changes were characterized by a cumulative function of the mass fraction of chains as a function of the root mean square end to end distance ( ) 2 1/2 0 r < > .

show abstract

“…A universal calibration was performed and the calibration curve was generated with monodisperse polystyrene (PS) standards (in the range 2·10 3 to 4·10 (Yau et al, 1979). The values of these constants used for the pairs PHB/chloroform and PS/chloroform, were respectively Κ= 1.18·10 -4 dL/g, α=0.794, and Κ= 4.9·10 -5 dL/g, α=0.78 (Kurata & Tsunashima, 1988). Sample injection volumes of 150 mL were used.…”

Section: Molecular Weight Determinationmentioning

confidence: 99%

Bacterial cellulose nanowhiskers to enhance the properties of plastics and bioplastics of interest in food packaging

Sanz¹

View full text Add to dashboard Cite

Viscosity – Molecular Weight Relationships and Unperturbed Dimensions of Linear Chain Molecules

Cited by 85 publications

References 831 publications

Further Investigation of Equilibrium Modulus of Diblock Copolymer Micellar Lattice

Further Investigation of Equilibrium Modulus of Diblock Copolymer Micellar Lattice

Caracterização viscosimétrica de nanocompósitos híbridos PS/POSS

Bacterial cellulose nanowhiskers to enhance the properties of plastics and bioplastics of interest in food packaging

Contact Info

Product

Resources

About