Shuichi Nojima

Crystallization of ε-caprolactone blocks within a crosslinked microdomain structure of poly(ε-caprolactone)-block-polybutadiene

Abstract The morphology, formed by the crystallization of e-caprolactone blocks in a crosslinked microdomain structure of poly(e-caprolactone)- block -polybutadiene (PCL- b -PB), has been investigated by wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), and differential scanning calorimetry (d.s.c.). The WAXD results showed that even in the crosslinked PCL- b -PB. PCL blocks crystallized in the same crystal form as PCL homopolymers. The SAXS measurements revealed that the microdomain structure in the melt remained unchanged by the subsequent crystallization, indicating that the PCL blocks crystallized within this structure. This point is extremely different from the case of the uncrosslinked PCL- b -PB, where a dramatic morphological reorganization takes place by the crystallization; a microdomain structure is completely replaced by an alternating structure of lamellae and amorphous layers. The melting temperature and crystallinity of the PCL blocks in the crosslinked PCL- b -PB were significantly reduced compared with those of the uncrosslinked PCL- b -PB, suggesting that the fixed microdomain structure affected significantly the crystallization of the PCL blocks to yield imperfect crystals within this structure.

Size dependence of crystallization within spherical microdomain structures

Abstract We have investigated the size dependence of crystallization within spherical microdomains formed in various poly(e-caprolactone)-block-polybutadiene diblock copolymers (PCL-b-PB). The crystallinity (χ) and melting temperature (Tm) of the PCL block are considerably lower than those of PCL homopolymer, and χ decreases steadily and Tm decreases only slightly with decreasing radius of PCL spheres (R) for a series of PCL-b-PB with a same molecular weight (Mn). When PCL-b-PB is compared with the similar R but different Mn, χ is significantly different, suggesting that the sphere size is not the unique factor to control crystallization within spherical microdomains.

Crystallization of block copolymers: 3. Crystallization behaviour of an ε-caprolactone-butadiene diblock copolymer

Abstract The crystallization behaviour of an e-caprolactone-block-butadiene diblock copolymer was observed by small-angle X-ray scattering employing synchrotron radiation. The processes of primary and secondary crystallizations were separately analysed by procedures usually used for homopolymer crystallization, and were compared with the case of a poly(e-caprolactone) homopolymer (PCL). The Avrami analysis at the primary crystallization showed an exponent n ranging from 2 to 3. This value is comparable to n evaluated for PCL and also n widely reported for crystalline homopolymers, indicating that the crystallization of the PCL block drives the primary stage without the influence of the existing microphase structure of the block copolymer. In the secondary crystallization, on the other hand, the rate was significantly retarded when a microphase structure existed in the system.

The effect of glass transition temperature on the crystallization of ε-caprolactone-styrene diblock copolymers

Abstract The morphology and melting behaviour of e-caprolactone-styrene diblock copolymers (PCL- b -PS) quenched from the melt were investigated by small-angle X-ray scattering and differential scanning calorimetry as a function of glass transition temperature of the PS block, T g , PS . A plasticizer miscible only with the PS block, such as polystyrene oligomer or dioctyl phthalate, was added to PCL- b -PS in order to decrease T g , PS successively (plasticizer-added PCL- b -PS). The crystallizability of the PCL block depended strongly on T g , PS ; the PCL block did not crystallize when T g , PS was higher than the crystallization temperature T c , while it crystallized partially when T g , PS was lower than T c . However, details of the morphology formed (i.e. the long spacing and lamellar thickness) were independent of T g , PS . These results suggest that the mobility of PCL- b -PS influences extremely the crystallizability of the PCL block, but not the resulting morphology. The morphologies formed in the plasticizer-added PCL- b -PS were compared with those of PCL- b -PS cast from toluene or cyclohexane solution, and the characteristics of these morphologies were qualitatively discussed.

Cubic phases of 4′-n-alkoxy-3′-nitrobiphenyl-4-carboxylic acids (ANBC-n)

The structure of the thermotropic cubic phases of 4′- n -alkoxy-3′-nitrobiphenyl-4-carboxylic acids (ANBC- n , where n indicates the number of carbon atoms in the alkoxy group) was studied by X-ray diffraction. For the homologues with n = 15, 16, 17, and 18, the cubic phase was of an Ia 3 d type, whereas the homologues with n = 19, 20, and 21 exhibited an Im 3 m cubic structure; for these seven homologues the same type of cubic structure was observed both on heating and cooling. Further lengthening of the alkoxy chain to n = 22 and 26, however, gave two types of cubic structure in the cubic phase region on heating, one with Im 3 m symmetry in the low temperature region and the other with Ia 3 d symmetry in the high temperature region. On cooling, the two homologues exhibited the Ia 3 d cubic structure only. This is the first example in the cubic phase region of a series of homologues containing two types of structure, dependent on temperature and n . Such a complicated phase diagram in the cubic region is clearly understood qualitatively in terms of Gibbs free energy-temperature diagrams. The dependence of structural parameters such as the cubic lattice constant on the alkoxy chain length n are also presented and discussed.

Cubic phases of binary systems of 4′-n-tetradecyloxy-3′-nitrobiphenyl-4-carboxylic acid (ANBC-14)-n-alkane

The phase behaviour of the binary systems 4′- n -tetradecyloxy-3′-nitrobiphenyl-4-carboxylic acid (ANBC-14)- n -alkane ( n -tetradecane or n -hexadecane) was investigated by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. The phase behaviour was a function of temperature ( T ) and the effective carbon number of the system ( n*), where n* involves carbon atoms both from the alkoxy group of ANBC-14 and from the n -alkane added. ANBC-14 shows no cubic phase, but the addition of n -alkane induced cubic phases when n*≧c. 15. An interesting point is that the type of cubic phase is Ia 3 d for 15≦n*≦17, while an Im 3 m type is formed for 18≦n*≦20. Furthermore, for n* = 22, two types of cubic phase, one with Im 3 m symmetry in the low temperature region and the other with Ia 3 d in the high temperature region, were observed both on heating and cooling. The phase diagram with respect to T and n* is very similar to that of pure one-component ANBC- n , which is a function of T and the number of carbon atoms in the alkoxy group n .

Small-angle X-ray scattering study of the morphology of blends of poly(ε-caprolactone) and polystyrene oligomer

Abstract A small-angle X-ray scattering (SAXS) study was carried out to investigate the morphology of blends of poly(e-caprolactone) (PCL) and polystyrene oligomer (PSO) when the former component was crystallized. This PCL-PSO system shows an upper critical solution temperature type of phase diagram. For blends with ф PCL ( ф PCL is the weight fraction of PCL), the scattering observed is the superposition of the intensities arising from the crystalline region (made up by alternate stacking of lamellae and thin amorphous layers) and from the inhomogeneity in the system (due to the crystalline regions and the amorphous domains). For blends with ф PCL > 0.8 , only scattering from the crystalline region was observed. From the SAXS curve, the lamella thickness lc, the amorphous layer thickness la and the linear crystallinity χc of the crystalline region were obtained on the basis of the Hosemann-Tsvankin model. The value of lc was 5.5 nm independent of composition, while la and χc were 8.1 nm and 0.4 for blends with ф PCL but varied linearly with composition for blends with ф PCL > 0.8 . These parameters were also studied by the correlation function from Vonks model.

Crystallization behaviour of a microphase-separated diblock copolymer

Abstract The crystallization behaviour of a microphase-separated diblock copolymer, ϵ-caprolactone-block-butadiene (PCL-b-PB), was observed by small-angle X-ray scattering employing synchrotron radiation. The Avrami analysis at the early stage of crystallization did not show any significant difference between PCL-b-PB and a poly(ϵ-caprolactone) homopolymer (PCL), suggesting that the initially existing microphase structure does not affect the early stage of crystallization. In the late stage, the crystallization of PCL-b-PB was significantly retarded compared to the case of PCL, and the rate was dependent on the microphase structure and/or molecular characteristics of the copolymer.

Effect of Component Mobility on the Properties of Macromolecular [2]Rotaxanes

Macromolecular [2]rotaxanes comprising a polymer axle and crown ether wheel were synthesized to evaluate the effect of component mobility on the properties of the axle polymer, especially its crystallinity. Living ring-opening polymerization of δ-valerolactone with a pseudorotaxane initiator with a hydroxy group at the axle terminus was followed by end-capping with a bulky isocyanate. This yielded macromolecular [2]rotaxanes (M2Rs) possessing polyester axles of varying molecular weights. The crystallinity of the axle polymers of two series of M2Rs, with either fixed and movable components, was evaluated by differential scanning calorimetry. The results revealed that the effect of component mobility was significant in the fixed and movable M2Rs with a certain axle length, thus suggesting that the properties of the axle polymer depend on the mobility of the polyrotaxane components.

X-ray Characterization of Two Cubic Phases and a Structured Liquid Phase of 4′-n-Alkoxy-3′-nitrobiphenyl-4-carboxylic Acids (ANBC-n)

Abstract The cubic D (CubD) and structured liquid (I1) phases of 4′-n-alkoxy-3′-nitrobiphenyl-4-carboxylic acids (ANBC-n, where n is the number of carbons in the alkoxy group) have been investigated by X-ray diffraction techniques. The type of the CubD phase was identified as Ia3d for the homologues with n=15, 19, 20, 22, and 26, similarly to those of n=16 and 18. On the basis of the model proposed by Luzzati and Spegt, the diameter (D/Å) and the length (L/Å) of the constituent rod are estimated and discussed. The structure of the I1 phase and its dependence on n are also discussed. For n=26, very surprisingly, another cubic phase with Im3m symmetry was observed at the lower temperature side of the Ia3d cubic phase on heating.