Hard phase glass transition

Our intentions with these block copolymers were to develop a microphase separated matrix, and differential scanning thermal analysis of the P[MG8-4VP] diblock copolymers indeed showed the presence of two glass transition temperatures indicating microphase separation. The thermal transitions for the block copolymers are listed in Table 4. Depending on the block copolymer composition, a soft (oxyethylene) phase glass transition temperature (Tg) is observed between -60 and -45°C and a hard (4-vinylpyridine) phase between 135 and 143 C. The slight lowering of the of the hard phase relative to the 150°C of pure poly(4-vinylpyridine) is due to internal plasticization of the hard phase by the short... 

Urethane structural adhesives have a morphology that is inverse to the toughened epoxy just described. The urethanes have a rubber continuous phase, with glass transition temperatures of approximately —50°C. This phase is referred to as the .soft segment . Often, a discontinuous plastic phase forms within the soft segment, and that plastic phase may even be partially crystalline. This is referred to as the hard segment . A representation of the morphology is shown in Fig. 3 [34]. 

Thermoplastic elastomers (TPE), 9 565-566, 24 695-720 applications for, 24 709-717 based on block copolymers, 24 697t based on graft copolymers, ionomers, and structures with core-shell morphologies, 24 699 based on hard polymer/elastomer combinations, 24 699t based on silicone rubber blends, 24 700 commercial production of, 24 705-708 economic aspects of, 24 708-709 elastomer phase in, 24 703 glass-transition and crystal melting temperatures of, 24 702t hard phase in, 24 703-704 health and safety factors related to, 24 717-718... 

The transition behavior of a number of liquid crystals with side-chain mesogens is summarized in Table 5. The most obvious feature of macromolecular liquid crystals is the frequent absence of fully ordered crystals at low temperatures. If fully ordered crystals are observed, crystallization is incomplete, i.e. the observed phase states are to be described by an area on the right side of Fig. 3. Glass transitions, which were hard to find in low molecular weight liquid crystals (see Table 3), are now prominent. 

Floudas and coworkers [90] employed dielectric spectroscopy to probe the interfacial width in lamellae forming non-linear block copolymers of the type (B-h-A)3B and (B-h-A)3B(A-h-B)3, where A is PI and B is PS. Their experiments were conducted at temperatures below the ODT and below the glass transition of the PS hard phase . In this temperature region the global chain dynamics of PI bridges were used to provide an estimate of the dynamic interface between... 

Block Size and Glass-Transition Temperatures of the Polystyrene Phase in Different Block Copolymers Containing Styrene Blocks as the Hard Phase... 

Those which do crystallise invariably do not form perfectly crystalline materials but instead are semi-crystalline with both crystalline and amorphous regions. The crystalline phases of such polymers are characterised by their melting temperature (TJ. Many thermoplastics are, however, completely amorphous and incapable of crystallisation, even upon annealing. Amorphous polymers (and amorphous phases of semi-crystalline polymers) are characterised by their glass transition temperature (T), the temperature at which they transform abruptly from the glassy state (hard) to the rubbery state (soft). This transition corresponds to the onset of chain motion below T the polymer chains are unable to move and are frozen in position. Both T and T increase with increasing chain stiffness and increasing forces of intermolecular attraction. 

---