Different approach for the correlation of the Tg of mixed amorphous systems

Pochan, J. M.; Beatty, C. L.; Pochan, D. F.

doi:10.1016/0032-3861(79)90128-9

Cited by 101 publications

(28 citation statements)

References 23 publications

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“…which is a logarithmic relationship formally empirically established by Pochan, Beatty and Pochan [23]. In these equations x and 9 are the weight and volume fraction, respectively and k a constant approximately equal to unity.…”

Section: Resultsmentioning

confidence: 99%

“…In these equations x and 9 are the weight and volume fraction, respectively and k a constant approximately equal to unity. The values calculated according to the above equations are coded Tgl, Tg, and Tg, in Table 3 where they are compared with the intermediate or single Tg found Table 3 Predicted and observed values of the glass transition temperature for the polystyrene 'polyisoprene mixed phase [20], [21] and [23], respectively. experimentally.…”

Section: Resultsmentioning

confidence: 99%

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Molecular-weight dependence of the glass transition temperatures of rigid SIS triblock copolymers studied by DSC

Widmaier¹,

Meyer²

1982

Journal of Thermal Analysis

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Differential scanning calorimetry (DSC) measurements have been carried out on a series of ABA poly(styrene-b-isoprene) triblock copolymers with 30% polyisoprene content and various molecular weights. The DSC data show an inward shift for the glass transition temperatures (Tg) of the blocks compared to the corresponding homopolymers. As a function of the molecular weight, one to three transitions were found. The additional third Tg gives some further evidence of the existence of an interphase between the microdomains.Numerous studies [1, 2] on multicomponent polymer systems have established the occurence of phase segregation and microdomain formation when two or more polymers are combined, in block copolymers, the factors governing the size of the domains depend on the number and length of the blocks and on their chemical nature.Meier [3] was the first to develop a theory about microphase formation for styrene-butadiene di-and triblock copolymers [4]. He showed that above a certain molecular weight, phase segregation takes place. Williams [5] and later Helfand [6] investigated the formation of an interphase: between the two pure phases, a region of mixed phases exists. These authors evaluated the influence of molecular weight and composition of the different blocks on the size of the pure phases and of the interphase. Particularly, the volume of the interphase increases with decreasing molecular weight. Toporowski and Roovers [7] as also Kraus and Rollmann [8] concluded that some low molecular weight block copolymers form a single phase. Through these investigations, block copolymers may exist in the solid state with morphologies going from a single phase to a completely organized two-phase structure.Glass transition temperatures (Tg) are commonly used to detect phase changes in copolymers. Two distinct Tg's corresponding roughly to those of the parent homopolymers appear when two well segregated phases exist in a copolymer. On the other hand, random copolymers known to exist as a single phase, show only one Tg, the value of which depends on its phase content. Thus, the number of transitions and the temperature at which they occur, provide information about the morphology of SIS copolymers.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Molecular-weight dependence of the glass transition temperatures of rigid SIS triblock copolymers studied by DSC

Widmaier¹,

Meyer²

1982

Journal of Thermal Analysis

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“…These values can be compared with the prediction from the Pochan equation [17] for random copolymers, which in the present case is:…”

Section: Differential Scanning Calorimetrymentioning

confidence: 96%

The influence of copolymerization with methacrylic acid on poly(butyl acrylate) film properties

Koh

Mange

Bothe

et al. 2006

Polymer

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“…All theories and models concerning polymerplasticizer blends assume that an intimate molecular mixture of the components is attained; otherwise, multiple glass transitions may be observed [90,102,151]. The simplest relation between the change in glass transition of a system upon adding a plasticizer is given as [151] T…”

Section: Effect Of Water and Other Plasticizersmentioning

confidence: 99%

A Review on Methods and Theories to Describe the Glass Transition Phenomenon: Applications in Food and Pharmaceutical Products

2009

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Given the complexity in composition and the various environmental conditions to which foods and pharmaceuticals are exposed during processing and storage, stability, functionality, and quality are key attributes that deserve careful attention. Quality and stability of foods and pharmaceuticals are mainly affected by environmental conditions such as temperature, humidity, and time, and for processing conditions (e.g., shear, pressure) under which they may undergo physical and chemical transformations. Glass transition is a key phenomenon which is useful to understand how external conditions affect physical changes on materials. Consequently, theories that predict and describe the glass transition phenomenon are of a great interest not only for the food industry but also it extends to the pharmaceutical and polymer industries. It is important to emphasize that the materials of relevance in these industries are interchangeably sharing similar issues on functionality and their association with the glass transition phenomenon. Development of new materials and understanding the physicochemical behavior of existing ones require a scientific foundation that translates into safe and high-quality foods, improved quality of pharmaceuticals and nutraceuticals with lower risk to patients, and functional efficacy of polymers used in food and medicinal products. This review addresses the glass transition phenomenon from a kinetics and thermodynamics standpoint by presenting existing models that are able to estimate the glass transition temperature. It also explores traditional and novel methods used for the characterization of the glass transition phenomenon.

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Different approach for the correlation of the Tg of mixed amorphous systems

Cited by 101 publications

References 23 publications

Molecular-weight dependence of the glass transition temperatures of rigid SIS triblock copolymers studied by DSC

Molecular-weight dependence of the glass transition temperatures of rigid SIS triblock copolymers studied by DSC

The influence of copolymerization with methacrylic acid on poly(butyl acrylate) film properties

A Review on Methods and Theories to Describe the Glass Transition Phenomenon: Applications in Food and Pharmaceutical Products

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