Dielectric normal mode spectroscopy in the ordered and disordered states of diblock copolymers

Stuehn, B.; Stickel, F.

doi:10.1021/ma00046a031

Cited by 46 publications

(48 citation statements)

References 12 publications

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“…The choice does not affect in a significant way the results obtained for the α-relaxation. This is in contrast with the results of Stünh and Stickel [26], who found values of γ that decreased with T for a polyisoprene-polystyrene copolymer. Schönhals [6] obtained molecular-weight-dependent values of γ for polyisoprene samples, which is at odds with the Rouse model predictions for type-A homopolymers.…”

Section: Copolymercontrasting

confidence: 99%

“…The normal and α modes merge very close to the calorimetric T g . Similar conclusions have been reached by Nicolai and Floudas for poly(oxypropylene) [26], and by Kyritsis et al for some poly(oxyethylene)-poly(oxybutylene) copolymers [18]. Figure 8 shows that a shift of the log 10 (τ ) of the normal mode makes the curve to overlap with the log 10 (τ ) for the α-relaxation for most of the temperature range; in fact only at T d = 217 K (i.e.…”

Section: The Normal Mode Relaxationsupporting

confidence: 89%

“…It has been found that for the β-relaxation γ = 1, i.e., the relaxation can be described by a Cole-Cole function. As has been discussed by Schönhals [6], and Stühn and Stickel [26] for pure type-A polymers, if the normal mode can be described by a Rouse-type dynamics, the normal mode should be characterized by δ = 1 and γ = 0.7. Adachi et al [17] have shown that for block copolymers in which type-A chains are diluted in non-type-A blocks the shape of the relaxation depends on the copolymer composition.…”

Section: Copolymermentioning

confidence: 92%

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Dielectric relaxation of poly(ethylenglycol)- b-poly(propylenglycol)-b-poly(ethylenglycol) copolymers above the glass transition temperature

Moreno

Rubio

Luengo

et al. 2001

The European Physical Journal E

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The complex dielectric permittivity has been measured for three poly(ethylenglycol)-bpoly(propylenglycol)-b-poly(ethylenglycol) copolymers with different content of poly(ethylenglycol) (15%, 33% and 80%), and increasing degree of crystallinity (0%, 10% and 20%, respectively). Only the noncrystalline sample shows the normal mode relaxation together with the segmental (α-relaxation) and the Johari-Goldstein (β-relaxation) modes. The crystalline samples show also polarization contributions due to the existence of interfaces between the crystallites and the amorphous phase. The relaxation times of the (α and normal modes can be described by a VFT equation with the same value of T 0. There is a slowing-down of the segmental mode due to the presence of crystallites. The temperature dependence of the α and β relaxations in the copolymers is very similar to that found in pure PPG, while there are significant differences in the case of the normal mode of the non-crystalline sample. The size of the cooperatively rearranging regions CRR, and the width of the glass transition region increase slightly with the degree of crystallinity. The temperature dependence of the size of CRRs is compatible with the prediction of fluctuation theory. No systematic effect of the degree of crystallinity on the β-relaxation has been found. Near T g the β-relaxation time is close to the primitive time of the coupling model.

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Section: Copolymercontrasting

confidence: 99%

Section: The Normal Mode Relaxationsupporting

confidence: 89%

Section: Copolymermentioning

confidence: 92%

See 1 more Smart Citation

Dielectric relaxation of poly(ethylenglycol)- b-poly(propylenglycol)-b-poly(ethylenglycol) copolymers above the glass transition temperature

Moreno

Rubio

Luengo

et al. 2001

The European Physical Journal E

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“…Furthermore, since in our case the weight fraction f PI of the polyisoprene block does not exceed 28%, the dielectric strength of the normal mode relaxation only is moderately pronounced or almost suppressed [2]. Dielectric spectroscopic data on SI diblock copolymers [73] also indicate that the segmental relaxation of the PI block can only be hardly seen for very low PI fractions or even not at all [74]. For low PI fractions, the dynamics of microphase separation can be terminated by the glass transition of the PS block such that no PI microdomain is developed and the normal mode of the PI block is not observed [74].…”

Section: Broadband Dielectric Spectroscopymentioning

confidence: 80%

Influence of block sequence and molecular weight on morphological, rheological and dielectric properties of weakly and strongly segregated styrene-isoprene triblock copolymers

Georgopanos

Handge

Abetz

et al. 2016

Polymer

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In this work, morphological, thermal, viscoelastic and dielectric properties of triblock copolymers consisting of styrene (S) and isoprene (I) blocks are discussed. SIS and ISI triblock copolymers were synthesized by sequential anionic polymerization, three of them exhibiting molecular weights below the entanglement molecular weight M e , three of them exhibiting molecular weights in the order of M e and two of them exhibiting molecular weights above M e . The objective of this work is the investigation of the influence of molecular weight and block sequence on relaxation of the block copolymer chains. Morphological investigations using small angle X-ray scattering and transmission electron microscopy studies reveal that a larger molecular weight is associated with a more pronounced microphase separation. The presence of two glass transition temperatures reveals microphase separation of the PI and PS blocks. The Fox-Flory equation was applied in order to describe the molecular weight dependence of the glass transition temperature of the polyisoprene and the polystyrene blocks. The analysis of rheological data reveals a Maxwell fluid behaviour for the weakly segregated block copolymers, whereas for the strongly segregated block copolymers a pronounced elastic behaviour at low frequencies of small amplitude shear oscillations was observed.In the intermediate regime of molecular weight, a complex viscoelastic behaviour appears. The plateau modulus G N o is influenced by the sequence of the PS and the PI blocks (SIS or ISI). Our analysis of segmental and normal mode relaxation in dielectric spectroscopy experiments show that the relaxation processes are strongly influenced by the block sequence (PI blocks tethered at one or 1 both ends) and the molecular weight. As a result, the block sequence in triblock copolymers influences dynamical properties in the glassy state and in the melt.

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“…The synthesis of a rigid polystyrene, characterized by a high glass transition point (T PS g ), with a mobile polyisoprene of a low (T PI g ) gives a product of parameters [3] controlled by composition of components and their molecular weight. Several dielectric [7][8][9][10][11][12][13] and NMR [14][15][16][17] experiments have been devoted to study the structure and molecular dynamics of polystyrene/polyisoprene diblock copolymers.…”

Section: Introductionmentioning

confidence: 99%

The phase structure and molecular dynamics in poly(styrene-b-isoprene) diblock copolymer

Jenczyk

Makrocka-Rydzyk

Wypych

et al. 2010

Journal of Non-Crystalline Solids

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Dielectric normal mode spectroscopy in the ordered and disordered states of diblock copolymers

Cited by 46 publications

References 12 publications

Dielectric relaxation of poly(ethylenglycol)- b-poly(propylenglycol)-b-poly(ethylenglycol) copolymers above the glass transition temperature

Dielectric relaxation of poly(ethylenglycol)- b-poly(propylenglycol)-b-poly(ethylenglycol) copolymers above the glass transition temperature

Influence of block sequence and molecular weight on morphological, rheological and dielectric properties of weakly and strongly segregated styrene-isoprene triblock copolymers

The phase structure and molecular dynamics in poly(styrene-b-isoprene) diblock copolymer

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