The effect of sequence distribution on glass transition in the theory of the cooperative Behaviour of random copolymers

1981 ◽  
Vol 4 (1-2) ◽  
pp. 9-16 ◽  
Author(s):  
Ivan Havlíček ◽  
Ján Biroš ◽  
Jiří Podešva ◽  
Jaroslav Hrouz
Keyword(s):  
Glass Transition ◽  
Random Copolymers ◽  
Cooperative Behaviour ◽  
Sequence Distribution

PVC/PBA random copolymers obtained by SET–DTLRP: Pressure effect on glass transition, rheology, and processing

2018 ◽  
Vol 25 (1) ◽  
pp. 76-84 ◽  
Author(s):  
Itxaso Calafel ◽  
Mercedes Fernández ◽  
Antxon Santamaría ◽  
Miquel Boix ◽  
Jose Ignacio Conde ◽  
...  
Keyword(s):  
Glass Transition ◽  
Pressure Effect ◽  
Random Copolymers

scholarly journals Competition between Structural Relaxation and Crystallization in the Glass Transition Range of Random Copolymers

Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1778
Author(s):  
Jürgen E. K. Schawe ◽  
Claus Wrana
Keyword(s):  
Glass Transition ◽  
Structural Relaxation ◽  
Random Sequence ◽  
High Sensitivity ◽  
Random Copolymers ◽  
High Time Resolution ◽  
Scanning Calorimetry ◽  
Transition Range ◽  
Glass Transition Range ◽  
And Control

Structural relaxation in polymers occurs at temperatures in the glass transition range and below. At these temperatures, crystallization is controlled by diffusion and nucleation. A sequential occurrence of structural relaxation, nucleation, and crystallization was observed for several homopolymers during annealing in the range of the glass transition. It is known from the literature that all of these processes are strongly influenced by geometrical confinements. The focus of our work is copolymers, in which the confinements are caused by the random sequence of monomer units in the polymer chain. We characterize the influence of these confinements on structure formation and relaxation in the vicinity of the glass transition. The measurements were performed with a hydrogenated nitrile-butadiene copolymer (HNBR). The kinetics of the structural relaxation and the crystallization was measured using fast differential scanning calorimetry (FDSC). This technique was selected because of the high sensitivity, the fast cooling rates, and the high time resolution. Crystallization in HNBR causes a segregation of non-crystallizable segments in the macromolecule. This yields a reduction in mobility in the vicinity of the formed crystals and as a consequence an increased amount of so-called “rigid amorphous fraction” (RAF). The RAF can be interpreted as self-assembled confinements, which limit and control the crystallization. An analysis of the crystallization and the relaxation shows that the kinetic of both is identical. This means that the Kohlrausch exponent of relaxation and the Avrami exponent of crystallization are identical. Therefore, the crystallization is not controlled by nucleation but by diffusion and is terminated by the formation of RAF.

Determining the Polydispersity in Chemical Composition and Monomer Sequence Distribution in Random Copolymers Prepared by Postpolymerization Modification of Homopolymers

2012 ◽  
Vol 1 (9) ◽  
pp. 1128-1133 ◽  
Author(s):  
Wayne Powers ◽  
Chang Y. Ryu ◽  
Young K. Jhon ◽  
Lawrence A. Strickland ◽  
Carol K. Hall ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Random Copolymers ◽  
Sequence Distribution ◽  
Monomer Sequence

Vinyl alcohol-vinyl propionate copolymers: sequence distribution and glass transition

Polymer ◽  
1988 ◽  
Vol 29 (12) ◽  
pp. 2244-2248 ◽  
Author(s):  
Manuel Sánchez-Chaves ◽  
Félix Arranz ◽  
Margarita Montes
Keyword(s):  
Glass Transition ◽  
Vinyl Alcohol ◽  
Sequence Distribution ◽  
Vinyl Propionate

The Role of Copolymer Architecture on the Interfacial Structure of a Ternary Polymer Blend

1996 ◽  
Vol 461 ◽  
Author(s):  
M. D. Dadmun
Keyword(s):  
Monte Carlo Simulation ◽  
Polymer Blend ◽  
Experimental Studies ◽  
Interfacial Structure ◽  
Random Copolymers ◽  
Random Structure ◽  
Sequence Distribution ◽  
Ternary Polymer ◽  
Interfacial Characteristics

ABSTRACTThe role of copolymer sequence distribution on the interfacial characteristics of a ternary polymer blend containing 2 homopoiymers and a copolymer in the phase separated state are examined using Monte Carlo Simulation. The copolymer does migrate to the biphasic interface in the phase separated regime while the configuration and expansion of the copolymer at the interface is a function of sequence distribution within the copolymer. This effect is interpreted in terms of the efficiency of the copolymer to strengthen the biphasic interface. These results suggest that block, alternating, and block-ran structures show promise as interfacial modifiers, while the purely random and alt-ran copolymers will be less efficient as an interfacial strengthener. It is also found that a variation of the sequence distribution away from a purely random structure can dramatically effect the ability of the copolymer to modify the interface. As most polymers which are not block nor alternating are termed ‘random’, this differentiation may have an effect on experimental studies of ‘random’ copolymers as compatibilizers in polymer blends.

Comb-like copolymers of n-alkyl monoitaconates and styrene

e-Polymers ◽  
2006 ◽  
Vol 6 (1) ◽  
Author(s):  
Helen Inciarte ◽  
Margie Orozco ◽  
Miladys Fuenmayor ◽  
Francisco López-Carrasquero ◽  
Haydee Oliva
Keyword(s):  
Glass Transition ◽  
Free Radical ◽  
Block Copolymers ◽  
Radical Polymerization ◽  
Alkyl Group ◽  
Molar Fraction ◽  
Melting Process ◽  
Side Length ◽  
Random Copolymers ◽  
Calorimetric Study

AbstractRandom and block copolymers containing styrene and mono n-alkyl itaconates with n = 12, 14, 16, 18 and 22 have been prepared by free radical polymerization and nitroxide-mediated radical polymerization. The molar fraction of the mono n-alkyl itaconate in block copolymers increased with increasing size of the alkyl group in the ester substituent. A calorimetric study of all these copolymers was performed. No glass transition (Tg) was observed in the temperature range - 30ºC-120ºC for random copolymers. Melting process attributed to crystalline order in the long side chains was observed for some copolymers depending on their composition and of the monoitaconate chain side length.

Alternating Copolymers by Complexed Copolymerization

1973 ◽  
Vol 46 (4) ◽  
pp. 1068-1076 ◽  
Author(s):  
M. Hirooka ◽  
K. Mashita ◽  
S. Imai ◽  
T. Kato
Keyword(s):  
Glass Transition ◽  
Physical And Mechanical Properties ◽  
Random Copolymer ◽  
Radical Copolymerization ◽  
Random Copolymers ◽  
Acrylonitrile Copolymer ◽  
Alternating Copolymers ◽  
Alternating Copolymer ◽  
Sequential Structure ◽  
Acrylic Ester

Abstract There have been few studies on how the nature of copolymers is affected by their sequential structure. This is because, in the past, the sequential structure of most copolymers could not be controlled at will. However, such studies have been realized since it was found that alternating sequential regulation can be attained from many monomer combinations, from which only random copolymers had been obtained previously, provided the copolymerization was carried out in the presence of a Lewis acid, such as an alkylaluminum halide. This kind of reaction is termed complexed copolymerization, as distinguished from the conventional alternating copolymerization. Furukawa and coworkers indicated that alternating butadiene—acrylonitrile copolymer is superior in various properties to the corresponding 1:1 random copolymer. Yabumoto and coworkers noticed that 1:1 styrene—acrylonitrile copolymer obtained in the presence of zinc chloride had a higher glass transition temperature than that of the corresponding 1:1 random copolymer made by radical copolymerization. Moreover, the former was hardly colored due to substantial absence of acrylonitrile—acrylonitrile bonds. Thus, it is very interesting how the properties of eopolymers are affected by sequential structure. The present paper describes various properties of alternating copolymers. The first part of this paper introduces a newly developed alternating copolymer of isobutylene and an acrylic ester and compares it with the corresponding homo-polymers. The latter part deals with comparison of alternating and random copolymers. Equimolar copolymers of styrene and acrylonitrile are compared in physical and mechanical properties. Glass transition temperatures of equimolar alternating and random copolymers of various vinyl compounds are compared. An interesting correlation is shown and discussed on the basis of a thermodynamic treatment.

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