Sequence Length Distribution in Segmented Block Copolymers

Peebles, L. H.

doi:10.1021/ma60042a034

Cited by 127 publications

(73 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Synthesis of TPUs normally produces a dergoing several different thermal treatments. This was carried out in an effort to elucidate the origin material with quite a broad hard segment length distribution, 40,41 meaning that the of multiple melting endotherms commonly encountered in DSC thermograms of polyetherurethanes development of ''ideal'' hard segment crystals as reported for some monodisperse incorporating MDI-BDO hard segments. In a previous study 36 involving morphological and physical model compounds is less likely in a TPU elastomer prepared in the usual manner.…”

Section: Introductionmentioning

confidence: 99%

The effect of average soft segment length on morphology and properties of a series of polyurethane elastomers. II. SAXS-DSC annealing study

Martin

Meijs

Gunatillake

et al. 1997

J. Appl. Polym. Sci.

169

119

View full text Add to dashboard Cite

A series of eight thermoplastic polyurethane elastomers were synthesized from 4,4-methylene diphenyl diisocyanate (MDI) and 1,4-butanediol (BDO) chain extender, with poly(hexamethylene oxide) (PHMO) macrodiol soft segments. The PHMO molecular weights employed ranged from 433 g/mol to 1180 g/mol. All materials contained 60% (w/w) of the macrodiol. The materials were characterized by differential scanning calorimetry (DSC) following up to nine different thermal treatments. In addition, three of the materials were selected for characterization by small-angle x-ray scattering (SAXS) following similar thermal treatments. The DSC experiments showed the existence of five hard segment melting regions (labelled T1-T5), which were postulated to result from the disordering or melting of sequences containing one to five MDIderived units, respectively. Evidence for urethane linkage dissociation and reassociation during annealing at temperatures above 150ЊC is presented. This process aids in the formation of higher melting structures. Annealing temperatures of 80-100ЊC provided the maximum SAXS scattering intensity values. Materials containing longer soft segments (and, therefore, longer hard segments) were observed to develop and sustain higher melting hard domain structures and also develop maximum average interdomain spacing values at higher annealing temperatures. Another additional series of three PHMO-based polyurethanes having narrower hard segment length distributions, was synthesized and characterized by DSC in the as-synthesized and annealed states. The resulting DSC endotherms provided further evidence to suggest that the T1-T5 endotherms were possibly due to melting of various hard segment length populations.

show abstract

Section: Introductionmentioning

confidence: 99%

The effect of average soft segment length on morphology and properties of a series of polyurethane elastomers. II. SAXS-DSC annealing study

Martin

Meijs

Gunatillake

et al. 1997

J. Appl. Polym. Sci.

169

119

View full text Add to dashboard Cite

show abstract

“…또한, 공중합 단계에서 친수성 소프트 세그멘트인 poly(ethylene glycol) (PEG)을 같이 도입하여 DMS에 의한 중합도 저하 및 방사성 문제를 해결하고 고분자 주쇄에 알 칼리 수용액의 침투를 용이하게 하여 알칼리 가수분해에 의한 감량을 보다 원활하게 해줄 수 있다고 알려져 있다 [5,10] [20,21]. [9,[17][18][19].…”

Section: 서 론unclassified

Effects of Molecular Weight of Poly(ethylene glycol) on the Thermal Properties and the Alkaline Hydrolysis of Copolyesters

Kim¹,

Jee²,

Lee³

et al. 2012

Textile Science and Engineering

View full text Add to dashboard Cite

Copolyesters containing sodium sulfonate group and poly(ethylene glycol) (PEG) were synthesized with various molecular weight of PEG. The selected molecular weights of PEG were 1000, 2000, 4000, 6000, and 16000. The thermal properties and the crystallization behaviors of the copolyesters were investigated by using differential scanning calorimeter (DSC). Alkaline hydrolysis of the copolyesters was studied as a function of the treatment time. The melting temperatures and the heats of fusion of the copolyesters increased with an increase in the PEG molecular weight, while the weight reduction rate of copolyesters in an alkaline solution decreased with an increase in the PEG molecular weight. At the same PEG content in copolyesters, hard segment length increases with the PEG molecular weight, which was thought to be the most important factor that determines the thermal properties and the alkaline hydrolysis behavior.

show abstract

“…At 80°C, this ratio was found equal to 0.5 (equal reactivity would imply k 2 : k 1 ϭ 1). More generally, using a formalism slightly different from the formalism of Peebles, 10 Nabeth et al 11 developed this kinetic scheme in order to describe the reaction between a diisocyanate and hydroxy-functional compounds by relating the initial OH-to-NCO ratio (r H ) to the reactivity ratio of k 2 to k 1 (or rather to the parameter S ϭ k 2 : 2k 1 ) and to the relative amount of residual diisocyanate molecules n id . Assuming that there was no side reaction, that all the once-reacted diisocyanate moieties had the same reactivity, whatever the molar mass of the molecule, and that all hydroxyl groups were equireactive, they found the following equation at full conversion of the OH groups:…”

Section: Isocyanate-terminated Prepolymersmentioning

confidence: 99%

New segmented polyurethane ureas based on 4,4?-dicyclohexylmethane diisocyanate and on various soft segments

Samson

Méchin

Pascault

1998

J. Appl. Polym. Sci.

View full text Add to dashboard Cite

Linear segmented polyurethane ureas were prepared from 4,4Ј-dicyclohexylmethane diisocyanate (H 12 MDI), 4,4Ј-diamino-3,3Ј-dicyclohexyl methane (3DCM), and various hydrophilic and hydrophobic soft segments. Kinetic studies of the synthesis of the diisocyanate-terminated prepolymers revealed that the use of too little reactive polyols (that is, polyoxypropylene that bears secondary hydroxyls) could be rather tricky; the noncatalyzed reaction is very slow, but the use of a catalyst soon triggers the formation of side products, and the processing window consequently becomes quite short. Microcalorimetric and dynamic mechanical measurements showed that all the materials were highly phase-segregated elastomers and displayed good mechanical properties up to high temperature (typically 180°C), provided that they had been postcured properly; in this respect, the dramatic effects of isolated (nonchemically linked) hard segments, as well as of too low postcuring temperatures, were demonstrated. Polyurethane ureas compare well with polyureas, and their synthesis can be a good way to cope with the lack of well-adapted commercial diamino-terminated prepolymers.

show abstract

Sequence Length Distribution in Segmented Block Copolymers

Cited by 127 publications

References 2 publications

The effect of average soft segment length on morphology and properties of a series of polyurethane elastomers. II. SAXS-DSC annealing study

The effect of average soft segment length on morphology and properties of a series of polyurethane elastomers. II. SAXS-DSC annealing study

Effects of Molecular Weight of Poly(ethylene glycol) on the Thermal Properties and the Alkaline Hydrolysis of Copolyesters

New segmented polyurethane ureas based on 4,4?-dicyclohexylmethane diisocyanate and on various soft segments

Contact Info

Product

Resources

About