Thermo-Rheological and Shape Memory Properties of Block and Random Copolymers of Lactide and ε-Caprolactone

Biodegradable block and random copolymers have attracted numerous research interests in different areas, due to their capability to provide a broad range of properties. In this paper, an efficient strategy has been reported for preparing biodegradable PCL-PLA copolymers with improved thermal, mechanical and rheological properties. Two block-copolymers are synthesized by sequential addition of the cyclic esters lactide (L-LA or D,L-LA) and ε-caprolactone (CL) in presence of a dimethyl(salicylaldiminato)aluminium compound. The random copolymer of L-LA and CL was synthetized by using the same catalyst. Chain structure, molar mass, thermal, rheological and mechanical properties are characterized by NMR, SEC, TGA, DSC, Rheometry and DMTA. Experimental results show that by changing the stereochemistry and monomer distribution of the copolymers it is possible to obtain a variety of properties. Promising shape-memory properties are also observed in the di-block copolymers characterized by the co-crystallization of CL and L-LA segments. These materials show great potential to substitute oil-based polymers for packaging, electronics, and medicine applications.

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Characterization of Block and Random Ethylene Propylene Copolymers by Differential Thermal Analysis

Rubber Chemistry and Technology ◽

10.5254/1.3547065 ◽

1966 ◽

Vol 39 (5) ◽

pp. 1513-1519

Author(s):

Edward M. Barrall ◽

Roger S. Porter ◽

Julian F. Johnson

Keyword(s):

Block Copolymers ◽

Freezing Point ◽

Random Copolymer ◽

High Heat ◽

Peak Height ◽

Chain Structure ◽

Heat Of Fusion ◽

Ethylene Content ◽

Point Data ◽

Physical Mixtures

Abstract DTA furnishes a reliable method for the analysis of physical mixtures and for multisegment and bisegment block copolymers of ethylene and propylene in cases where chain randomness is minor. If a secondary method of analysis which is independent of crystallinity is possible, e.g., use of C14-tagged samples, the DTA method can aid in elucidating the chain structure, including degree of copolymer randomness. Block copolymers and physical mixtures have been found to have thermograms with endothermal minima at approximately 138 and 163° C. The ratio of heights of the two minima has been found to be a function of the ethylene and propylene content for mixtures of homopolymers and for block copolymers without randomnness. Cooling thermograms of block copolymers have been demonstrated to have two exotherms in all cases where the block ethylene content exceeded 10 per cent; the propylene limit was not fixed. Mixed homopolymers do not exhibit two freezing exotherms. The total heat of fusion of the polymer has been found to be a usable measure of chain randomness and block nature. Conditions for observation of single and multiple transitions have been extended. The following conclusions can be drawn from Table I. Multisegment block copolymers are characterized by heats of fusion almost equal to or lower than corresponding physical mixtures. Bisegment block copolymers have heats of fusion equivalent to physical mixtures within experimental error. Cooling curves definitely indicate that samples 3–6 and 3–13 are block copolymers according to Ke's criterion of double exotherms. Sample 3–3 may be inferred to have a large amount of randomness between blocks from its low heat of fusion, which is comparable to that of polymers with known randomness. Samples 3–35 and 3–40 are both block copolymers by the double freezing point technique. The block copolymer identification and the high heat of fusion (almost as large as a comparable physical mixture) indicate long block length and only a few blocks. Very little randomness is present (compare data of Figure 2). Low heats of fusion consistent with short block segments in sequential arrangement are noted for samples 3–30 and 3–31. No confirmation of the block nature can be obtained from freezing point data due to low ethylene content. The displacement from curve in Figure 2 indicates noncrystalline segments in the chain. Multisegment block copolymers are identified from heat of fusion data and freezing point thermograms; note samples 3–32, 3–33, and 3–34. The location of the peak height ratios in Figure 2 indicates the presence of random copolymer with some crystallinity between blocks in all cases.

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Synthesis and Properties of Copolymers of Diphenylsiloxane with Other Organosiloxanes

MRS Proceedings ◽

10.1557/proc-171-105 ◽

1989 ◽

Vol 171 ◽

Cited By ~ 2

Author(s):

J. Ibemesi ◽

N. Gvozdic ◽

M. Kuemin ◽

Y. Tarshiani ◽

D. J. Meier

Keyword(s):

Block Copolymers ◽

Physical Properties ◽

Liquid Crystalline ◽

Elastic Solid ◽

Random Copolymer ◽

Random Copolymers ◽

Crystalline Solid ◽

Sequence Length ◽

Molar Ratios ◽

Star Block Copolymers

ABSTRACTWe describe the synthesis, characterization and properties of various types of siloxane polymers containing diphenylsiloxane (P) as a component. The polymer types include di-and tri-block copolymers with dimethylsiloxane (M) as the second component, and random and statistical copolymers with dimethylsiloxane or methylphenylsiloxane (P/M) as the second component. Such copolymers combine siloxane units whose polymers have very different properties. The polydiphenylsiloxane chain is rigid and inflexible, and the polymer is a highly crystalline solid with a liquid crystalline or condis crystalline state and a very high melting (clearing) temperature. In contrast, the polydimethylsiloxane or polymethylphenylsiloxane chains are very flexible and the polymers have very low glass transition temperatures.Polymers of controlled molecular composition, size and architecture were prepared by anionic polymerization of the ‘cyclic trimers’, using lithium-based initiators.The physical properties of the copolymers vary dramatically with composition and architecture. Two types of ‘random’ copolymers can be prepared. In one type, siloxane units of a given type are randomly placed in the chain in groups of three, i.e., the minimum sequence length of a given siloxane type is three siloxane units. In the other type of random copolymer, individual siloxane units are randomly distributed so that the minimum sequence length is a single siloxane unit. The properties of the two types are quite different, showing that subtle changes in sequence distribution can have major effects on physical properties. At molar ratios near 1/1 and with molecular weights of ∼105, the first type of ‘random’ copolymer is an elastic solid with appreciable mechanical properties, whereas the latter type is a sticky gum.Diblock copolymer (P-M) with dimethylsiloxane as the major component are paste-like, whereas the triblock (P-M-P) and star-block copolymers of the same composition are tough elastomers. The block copolymers are molecular composites, in which the polydiphenylsiloxane component separates into crystalline microphases with very uniform fibrillar or lamellar morphologies, and with widths or thicknesses comparable to the length of the polydiphenylsiloxane block, i.e, typically of the order of 100 Å.

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Enhanced mechanical and shape memory properties of polyurethane block copolymers chain-extended by ethylene diamine

European Polymer Journal ◽

10.1016/j.eurpolymj.2006.08.013 ◽

2006 ◽

Vol 42 (12) ◽

pp. 3367-3373 ◽

Cited By ~ 49

Author(s):

Byoung Chul Chun ◽

Tae Keun Cho ◽

Yong-Chan Chung

Keyword(s):

Block Copolymers ◽

Shape Memory ◽

Ethylene Diamine ◽

Shape Memory Properties

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Thermoresponsive aggregation behavior of NiPAAm/glyco monomer block copolymers studied by dynamic light scattering

e-Polymers ◽

10.1515/epoly.2010.10.1.482 ◽

2010 ◽

Vol 10 (1) ◽

Cited By ~ 1

Author(s):

Zeynep Özyürek ◽

Brigitte Voit ◽

Franziska Krahl ◽

Karl-Friedrich Arndt

Keyword(s):

Phase Transition ◽

Transition Temperature ◽

Block Copolymers ◽

Random Copolymer ◽

Aggregation Behavior ◽

Molar Ratio ◽

Random Copolymers ◽

Temperature Dependent ◽

Lcst Behavior ◽

Monomer Content

AbstractBlock and random copolymers containing N-isopropylacrylamide and (α- D-glucofuranosyl)-6-methacrylamido units were analyzed according to their temperature dependent aggregation behavior. Whereas a 45:55 random copolymer does not exhibit any LCST behavior below 100 °C due to the incorporation of the hydrophilic glyco monomer units, the phase transition could be retained in the physiological range in block copolymers even at a glyco monomer content above 55 mol%. DSL studies revealed that the aggregates of about 50 nm are stabilized above the transition temperature when the glyco monomer block dominates, whereas a glyco block molar ratio of 45% is not sufficient to prevent precipitation of the polymers as evidenced by turbidity measurements. Temperature dependent DLS studies revealed further that below the phase transition temperature an equilibrium between single macromolecules and aggregates is formed.

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Effect of calcium ion implantation and of immersion in Hank's solution on shape memory properties of Ti-Ni alloy

Journal de Physique IV (Proceedings) ◽

10.1051/jp4:20031079 ◽

2003 ◽

Vol 112 ◽

pp. 1121-1124

Author(s):

T. Asaoka ◽

S. Nakazawa

Keyword(s):

Ion Implantation ◽

Shape Memory ◽

Calcium Ion ◽

Ni Alloy ◽

Shape Memory Properties ◽

Hank’S Solution

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Thermo‐responsive shape memory properties based on polylactic acid and styrene‐butadiene‐styrene block copolymer

Journal of Applied Polymer Science ◽

10.1002/app.51000 ◽

2021 ◽

pp. 51000

Author(s):

Fathin Hani Azizul Rahim ◽

Abdul Aziz Saleh ◽

Raa Khimi Shuib ◽

Ku Marsilla Ku Ishak ◽

Zuratul Ain Abdul Hamid ◽

...

Keyword(s):

Block Copolymer ◽

Shape Memory ◽

Polylactic Acid ◽

Shape Memory Properties ◽

Styrene Butadiene Styrene ◽

Styrene Butadiene ◽

Butadiene Styrene

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Shape memory properties and microstructural evolution of rapidly solidified CuAlBe alloys

Materials Characterization ◽

10.1016/j.matchar.2013.03.010 ◽

2013 ◽

Vol 80 ◽

pp. 92-97 ◽

Cited By ~ 6

Author(s):

Semra Ergen ◽

Orhan Uzun ◽

Fikret Yilmaz ◽

M. Fatih Kiliçaslan

Keyword(s):

Shape Memory ◽

Microstructural Evolution ◽

Shape Memory Properties ◽

Rapidly Solidified

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Shape Memory NiTi and NiTiCu Alloys Obtained by Spark Plasma Sintering Process

Advanced Engineering Forum ◽

10.4028/www.scientific.net/aef.13.83 ◽

2015 ◽

Vol 13 ◽

pp. 83-90 ◽

Cited By ~ 3

Author(s):

Cristiana Diana Cristea ◽

Magdalena Lungu ◽

Alexander M. Balagurov ◽

Virgil Marinescu ◽

Otilia Culicov ◽

...

Keyword(s):

Shape Memory ◽

Intermetallic Compounds ◽

Spark Plasma Sintering ◽

Sintering Process ◽

Transformation Behavior ◽

Plasma Sintering ◽

New Process ◽

Shape Memory Properties ◽

Spark Plasma ◽

Niti Shape Memory Alloys

The addition of Cu to near equiatomic NiTi shape memory alloys (SMAs) can provide some modifications of their shape memory properties by affecting their transformation behavior. The same effect was obtained in the case of Ni3Ti2 and Ni4Ti3 precipitates presence in the microstructure of NiTi. Also the substitution of Cu to NiTi alloys increases the hardness of the materials. This paper presents the microstructural and mechanical investigations of NiTi and NiTiCu alloys obtained by spark plasma sintering (SPS) process that represents a great potential for researchers as a new process for the fabrication of intermetallic compounds.

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