Crystallization and melting behavior of the soft and hard segments in poly(ester-ether)s. II. Ethylene oxide-butylene terephthalate segmented copolymers

The crystallization behavior of a series of ethylene oxide-butylene terephthalate (EOBT) segmented copolymers with different soft segment molecular weight and hard segment weight content were examined by differential scanning calorimeter (DSC) and polarized microscope. Combined with the comparison with the crystallization behavior of ethylene oxide-ethylene terephthalate (EOET) segmented copolymers, it can be concluded that the crystallizability of both the soft segments and the hard segments in poly(ester-ether) segmented copolymers is much worse than those of the corresponding homopolymers due to the interactions between the soft and the hard segments. The crystallizability of the soft segments is mainly determined by the soft segment molecular weight, but is weakened by the hard segments. On the other hand, the soft segments have complicated influences on the crystallization of the hard segments. The melting temperatures of the hard segments change monotonically with the average hard segment length, but the corresponding melting enthalpies will reach a maximum at an intermediate soft segment molecular weight. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2928–2940, 1999     

Rheological characterization and microphase‐separated structure of a poly(ether‐block‐amide) segmented block copolymer

Melt of a segmented block copolymer having poly(lauryl lactam) as the hard segment and poly(tetramethylene oxide) as the soft segment was investigated by rheological techniques. Storage modulus of the polymer melt exhibits the nonterminal behavior resembling those of diblock and triblock copolymer melts, indicating the existence of a microphase‐separated structure. Contrary to block copolymers, the melt of the segmented block copolymer changes from a weak structure to a stiff one upon raising temperature. The storage modulus of the weak structure at low temperatures is inert to large‐amplitude oscillatory shear, while the oscillatory shear destroys the stiff structure at high temperatures and reduces its storage modulus to a value that is same as that of the weak structure. The tapping‐mode data of atomic force microscopy reveal that at low temperatures the polymer melt exhibits a biphasic structure consisted of small spherical soft domains dispersed in a slightly harder matrix; and at high temperatures the spherical domain structure preserves, though the domain coarsens and the hardness difference between the domain and the matrix enlarges. Infrared spectrum analysis shows that the temperature‐induced structural change is related to the dissociation of hydrogen bonding between the hard and soft segments. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2557–2567, 2005     

Crystallization and melting behavior of the soft and hard segments in poly(ester-ether)s. I. Ethylene oxide-ethylene terephthalate segmented copolymers

The crystallization and melting behavior of a series of ethylene oxide-ethylene terephthalate (EOET) segmented copolymers with different soft segment molecular weight and hard segment weight content were studied by differential scanning calorimeter (DSC) and polarized microscope. The crystallizability of both the hard and the soft segments became worse than that of the corresponding homopolymers due to the interactions of the different segments. The crystallizability of the soft segments is mainly determined by the soft segment molecular weight, but is affected greatly by the content and the crystallinity of the hard segments. Conversely, the soft segment length and content also have a great effect on the crystallization of the hard segments. However, the melting points of the hard segments are determined by the average hard segment length. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2918–2927, 1999     

Structure-property relationships in polycaprolactone-polyurethanes

The structure-property relationships of polycaprolactone-based segmented polyurethanes were studied using differential scanning calorimetry (DSC), small-angle x-ray scattering (SAXS), wide-angle x-ray diffraction (WAXD), dynamic mechanical, and stress-strain testing. The materials studied varied in hard-segment type [4,4′-diphenylmethane diisocyanate/butanediol (MDI/BD) or 4,4′-dicyclohexyl methane diisocyanate/butanediol (H₁₂MDI/BD)], soft-segment molecular weight (830 or 2000 MW polycaprolactone), hard-segment content (23–77% by weight), and thermal history. The materials with aromatic (MDI/BD) hard segments had semicrystalline hard-segment domains, while the materials with aliphatic (H₁₂MDI/BD) hard segment had mostly amorphous domains. Materials with the shorter polycaprolactone soft segment (830 MW) exhibited thermal and mechanical behavior which indicated a considerable degree of hard- and soft-segment compatibility. The materials which contained a 2000-MW polycaprolactone soft segment exhibited better-defined microphase separation. SAXS was used to characterize the microphase structure of each system. The effects of hard-segment content and soft-segment molecular weight were similar for the aromatic (MDI) and aliphatic (H₁₂MDI) hard-segment-based block copolymers. Changing the hard segment from aromatic to aliphatic gave materials with larger interfacial area and slightly higher tensile strength. A range of morphologies between isolated hard domains in a rubbery matrix and isolated rubbery domains in a hard matrix was observed.     

Segmented polyurethanes derived from novel siloxane–carbonate soft segments for biomedical applications

A novel macrodiol based on mixed silicone and carbonate chemistries was synthesized and used as a soft segment precursor in the synthesis of two series of segmented polyurethane (PU) copolymers varying in hard segment content and soft segment molecular weight. The hard segments in these copolymers were derived from 4,4‐methylene diphenyl diisocyanate and 1,4‐butane diol. The phase transitions, microphase separation behavior, and mechanical properties of the copolymers were investigated using a variety of experimental methods. When compared with segmented PU copolymers having predominately poly(dimethyl siloxane) soft segments, these siloxane–carbonate soft segment copolymers exhibit enhanced intersegment mixing, and consequently relatively low mechanical modulus. With relatively low modulus and siloxane units in the soft phase, the siloxane–carbonate PUs have potential for use in cardiac and orthopedic biomedical applications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Polyether-polyester and HMDI Based Polyurethanes:Effect of PLLA Content on Structure and Property

Thermoplastic poly(ether-ester-urethane)s were synthesized from poly(L-lactide) diols (PLLA diols),polytetrahydrofuran diol(PTMG diols),4,4'-dicyclohexylmetlhane diisocyanate (HMDI),and 1,4-butanediol (BDO) by a two-step reaction,and the morphology and property of the resultant TPU could be adjusted by varying the PLLA contents.The soft segment was composed of PLLA and PTMG diols.By controlling the percentage of PLLA in the soft segment,the glass transition temperature and mechanical properties of the polyurethanes could be regulated.Based on the FTIR spectrum,we found that two kinds of hydrogen bonding existed individually in soft matrix and hard domain.The hydrogen bonding in soft matrix was unstable,which could be destroyed during elongation.With in situ stretching WAXS and SAXS experiments,we found that the PLLA crystal was destroyed and the PLLA domain oriented along the stretch direction.Finally,we proposed a schematic model to illustrate the microstructures of these elastomers before and after stretch.     

Theoretical modeling of the relationship between Young's modulus and formulation variables for segmented polyurethanes

We describe a new modeling approach to prediction of Young's modulus of segmented polyurethanes. This approach combines micromechanical models with thermodynamic considerations based on the theory of block copolymers. The resulting model predicts both the equilibrium morphology and the “ideal” Young's modulus of a segmented polyurethane polymer as a function of its formulation (hard segment chemical structure, hard segment weight fraction, soft segment equivalent weight) and temperature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2123–2135, 2007     

Structure and deformation recovery of the thermoplastic polyurethane spherulite

We investigated the structure and deformation behavior of the thermoplastic polyurethane (TPU) spherulite by optical microscopy, tensile testing, Hv light scattering, and small angle X‐ray scattering. The TPU spherulite structure obtained by melt crystallization was coarse consisting of bundle‐like structure containing hard segment (HS) lamellar domain in which the HS domains were stacked and the HS chain direction was perpendicular to the longitudinal axis of the HS domain. By stretching, the spherulite was deformed to ellipsoidal one and the stacked HS lamellar domains were tilted in the stretching direction. The deformed spherulite and the tilted HS domain in the spherulite were recovered to the unstretched state by retraction. The recovery of the structure is ascribed to the characteristic spherulite structure consisting of rubbery soft segment matrix physically cross‐linked with the stacked HS domain. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1585–1594     

Synthesis and characterization of poly(dimethylsiloxane‐urethane) elastomers: Effect of hard segments of polyurethane on morphological and mechanical properties

A series of poly(dimethylsiloxane‐urethane) elastomers based on hexamethylenediisocyanate, toluenediisocyanate, or 4,4′‐methylenediphenyldiisocyanate hard segment and polydimethylsiloxane (PDMS) soft segment were synthesized. In this study, a new type of soft‐segmented PDMS crosslinker was synthesized by hydrosilylation reaction of 2‐allyloxyethanol with polyhydromethylsiloxane, using Karstedt's catalyst. The synthesized soft‐segmented crosslinker was characterized by FT‐IR, ¹H, and ¹³C NMR spectroscopic techniques. The mechanical and thermal properties of elastomers were characterized using tensile testing, thermogravimetric analysis, differential scanning calorimetry (DSC), and dynamical mechanical analysis measurements. The molecular structure of poly(dimethylsiloxane‐urethane) membranes was characterized by ATR‐FTIR spectroscopic techniques. Infrared spectra indicated the formation of urethane/urea aggregates and hydrogen bonding between the hard and soft domains. Better mechanical and thermal properties of the elastomers were observed. The restriction of chain mobility has been shown by the formation of hydrogen bonding in the soft and hard segment domains, resulting in the increase in the glass‐transition temperature of soft segments. DSC analysis indicates the phase separation of the hard and soft domains. The storage modulus (E′) of the elastomers was increasing with increase in the number of urethane connections between the hard and soft segments. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2980–2989, 2006     

聚醚氨酯的微区形态

<正> 聚醚氨酯热塑弹性体是属于(AB)n类型的线型多嵌段共聚物,包括交替的硬段和软段单元.自从1966年Cooper和Tobolsky首先提出聚氨酯具有微相分离的本体结构之假设以后,至今已有大量文献报道了这类材料结构形态与性能关系的研究结果. Wilkes和Koberstein等使用SAXS研究了聚氨酯体系的形态特征.一般认为,聚氨酯材料的微相结构包括一个叠层状或类似叠层状形态,由相分离的软段和硬段组成,平均尺寸为100A的数量级,在软硬段微区之间还存在一相混合的过渡区,其厚度可以从几个埃至几十个埃.然而,SAXS虽然能够高分辨地给出多相体系相分离情况的定     

Segmental and chain orientational behavior of spandex fibers

The internal structure and orientation behavior of two series of spandex fibers, which were made with different spinning methods and different soft and hard segment types, were studied by FTIR (Fourier Transform Infrared Spectroscopy), polarizing light microscopy, and Instron. The orientation behavior of hard and soft segments was studied with FTIR and those of polymeric chains with polarizing miscroscopy while the fibers were being stretched by the mechanical stretcher. The orientation behavior of dry-spun fibers was observed to be very different from that of the melt-spun fibers, which may be explained in terms of the internal structural difference such as the degree of phase separation and mechanical stability of the hard domains between the two types of fibers. In general, the dry-spun fibers showed better elastic recovery property than the melt-spun fibers. Since the polymer for the dry-spun fibers was synthesized with ethylene diamine as a chain extender resulting in the urea groups in the hard segments, it forms more stable hard domain due to the high cohesion energy between the urea groups. The change of the birefringence values during the cyclic deformation was studied with the polarizing light microscopy. The birefringence behaviors of the two dry-spun fibers were similar, whereas there was a noticeable difference between the two melt-spun fibers. The difference was explained in terms of the effect of crosslinking agent in one of the melt-spun fibers, which can stabilize the hard domain structure against the external stress. Mechanical hysteresis values measured gave results consistent with those of FTIR and birefringence measurements. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1821–1832, 1997     

Structure and properties of segmented poly(urethaneurea)s with relatively short hard‐segment chains

We report the structure and properties of segmented poly(urethaneurea) (SPUU) with relatively short hard‐segment chains. The SPUU samples comprised poly(tetramethylene glycol) prepolymer as a soft segment and 4,4′‐diphenylmethane diisocyanate (MDI) units as a hard segment that were extended with ethylenediamine. To discuss quantitatively the conformation of the soft‐segment chain in the microphase‐separated domain space, we used SPUU samples for which the molecular weights of the hard‐ and soft‐segment chains are well characterized. The effects of the cohesive force in the hard‐segment chains on the structure and properties of SPUU were also studied with samples of different chain lengths of the hard segment, although the window of x_H, the average number of MDI units in a hard‐segment chain, was narrow (2.38 ≤ x_H ≤ 2.77). There were urethane groups in the soft segments and urea groups in the hard segments. Because of a strong cohesive force between the urea groups, we could control the overall cohesive force in the hard‐segment chains by controlling the chain lengths of the hard segment. First of all, microphase separation was found to be better developed in the samples with longer hard‐segment chains because of an increase of the cohesive force. It was also found that the interfacial thickness became thinner. The long spacing for the one‐dimensionally repeating hard‐ and soft‐segment domains could be well correlated with the molecular characteristics when the assumption of Gaussian conformation was employed for the soft‐segment chains. This is unusual for strongly segregated block copolymers and might be characteristic of multiblock copolymers containing rod–coil chains. The tensile moduli and thermal stability temperature, T_H, increased with an increase of the cohesive force, whereas the glass‐transition temperature, the melting temperature, and the degree of crystallinity of the soft‐segment chains decreased. The increase in T_H especially was appreciable, although the variation in the chain length of the hard segment was not profound. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1716–1728, 2000     

COMPOSITIONAL HETEROGENEITY OF ETHYLENE OXIDE-BUTYLENE TEREPHTHALATE SEGMENTED COPOLYMER*

A series of ethylene oxide-butylene terephthalate (EOBT) segmented copolymers with differentsoft segment length and hard segment content were synthesized. The compositional heterogeneity was studiedby solvent extraction. The results show that the compositional heterogeneity increases when soft segmentlength and hard segment content increase. The compositional heterogeneity is also reflected in thecrystallization behavior and morphology of soft and hard segment in EOBT segmented copolymer. The morecompositional heterogeneous the EOBT segmented copolymer is, the more different the morphology and thecrystallization behavior between separated fractions. Compared with ethylene oxide-ethylene terephthalate(EOET) segmented copolymer, compositional heterogeneity in EOBT segmented copolymer is weaker. Butthe compositional heterogeneity in EOBT segmented copolymer with long soft segment and high hardsegment content is still obvious.     

New fluorinated thermoplastic elastomers. II. Synthesis and characterization of perfectly alternating fluorinated polyimide–fluorinated polyhybridsiloxane block copolymers via polyhydrosilylation

The synthesis of perfectly alternating fluorinated polyimide–fluorinated polyhybridsiloxane block copolymers (FPI‐FPHSX) was achieved through polyhydrosilylation of α,ω‐diallylfluorinated polyimides (AT‐FPI) and α,ω‐dihydrosilane fluorinated–polyhybridsiloxanes (HT‐FPHSX). A series of three FPI‐FPHSX containing 15, 38, and 56 wt % of polyimide was synthesized and characterized by tuning the number‐average molecular weight either of the hard polyimide segments or of the soft polyhybridsiloxane segments. The influence of the soft and hard segment lengths on the behavior of the thermoplastic elastomer material was studied (hardness, surface tension, thermal stability). The FPI‐FPHSX block copolymers thermomechanical properties are also reported. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 200–207, 2004     

聚硅氧烷聚脲多嵌段共聚物中氢键的研究

采用多种手段研究了聚硅氧烷与聚脲嵌段共聚物中所存在的各类氢键．特别探讨在聚硅氧烷软段中引入极性氰丙基对体系成氢键能力的影响和两相间相互作用力的情况结果表明，在软段分子中引入极性氰丙基有利于增加聚硅氧烷分子与聚脲链段的相互作用，这一相间作用力使两相间界面层厚度随着硬段分子量的增加而加宽，并发现在聚硅氧烷聚脲嵌段共聚物中硬段的聚集形态随溶液浓度改变变化不大，其中氢键随着温度升高而下降．     

THE RHEO-OPTICAL FTIR STUDY OF POLYESTERPOLYETHER SEGMENTED COPOLYMER

The polyester-polyetber segmented copolymer has been investigated by rheo-optical FTIR during stretehing for the informastion on strain induced crystallizatinn of soft segment chains, hard and soft chain orientation.At room temperature 15℃, the soft segment chains of polyester-polyether being to crystallize at 220% strain and the degree of crystallixation increa(?)e with draw ratio, but there will not be any soft segment chains crystallization above 21℃even at bigber strain. The average orientation of hard segment chains are higher than that of the soft chain at high strain level, both are positive oriented into the stretching direction at allover strain level. This indicates that the b(?)d (?)ent ch(?)ins are dispersed into the elastomeric phase and without forming spherulite.     

聚硅氧烷聚脲嵌段共聚物的TEM及SAXS研究

采用透射电子显微镜与小角X光散射分别研究了不同软、硬段分子量及软段极性对聚硅氧烷聚脲多嵌段共聚体系微相结构的影响。结果表明,增加软段分子量及硬段含量有利于聚硅氧烷与聚脲的相分离。将极性氰丙基引入聚硅氧烷后两相混合度明显改善,同时聚脲硬段粒径减小并趋于均一。在聚氰丙基甲基硅氧烷基体中增加聚脲含量及其分子量,则两相界面厚度也随之增大。     

Microstructure evolution during tensile loading histories of a polyurea

The evolution in the hard/soft domain microstructure of an elastomeric‐like polyurea during different tensile loading histories was studied using in situ small‐ and wide‐angle X‐ray scattering (SAXS/WAXS). The nonlinear stress–strain behavior is initially stiff with a rollover yield to a more compliant response; unloading is highly nonlinear showing substantial hysteresis while also exhibiting significant recovery. Reloading reveals a substantially more compliant “softened” behavior and dramatically reduced hysteresis. WAXS peaks monitor characteristic dimensions of regular features within the hard domains; the peak location remains unchanged with tensile deformation indicating no separation of the internal structure within a domain, but the peak intensity becomes anisotropic with deformation evolving in a reversible manner consistent with orientation due to stretch. The SAXS profiles provide information between major hard domains. SAXS peaks are found to shift with tensile loading in a relatively affine manner up to a tensile true strain of ～0.4, which, using a Bragg reduction to aid interpretation, reveals an axial increase and a transverse decrease in interdomain spacings; this evolution is reversible for strains less than ～0.4. Increasing axial strain beyond a true strain of ～0.4 is accompanied by a dramatic, progressive, and irreversible reduction in axial Bragg spacing, indicating a breakdown in the hard domain aggregate network structure. A four‐point pattern is seen to develop during stretching. The breakdown in networked structure during a first load cycle gives a new structure for subsequent load cycles, which is seen to evolve in a reversible manner for strains less than or equal to the prior maximum strain. However, for strains exceeding the prior maximum strain excursion, additional breakdown is found. These SAXS results show that a breakdown in the hard domain aggregate network structure is a governing mechanism for the large dissipation (hysteresis) loops of the first load cycle and are also responsible for the softened reloading response. The absence of structure breakdown during subsequent load cycles corresponds to the substantially reduced hysteresis loops as well as the stable softened behavior. DMA data on pristine and previously deformed samples show a more compliant storage modulus in the predeformed sample, supporting the softened cyclic stress–strain data and the structural breakdown observed in the SAXS; the loss modulus was unchanged with deformation, which correlates with the lossy features measured in DMA with time‐dependent viscosity rather than losses due to structural breakdown. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Poly(chloropropylmethyl-dimethylsiloxane)–polyurethane elastomers: Synthesis and properties of segmented copolymers and related zwitterionomers

A series of polyurethane block copolymers based on hydroxybutyl terminated poly(chloropropylmethyl-dimethylsiloxane) and poly(tetramethylene oxide) soft segments of molecular weights 2100 and 2000, respectively, were synthesized. The hard segments consisted of 4,4′-methylenediphenylene diisocyanate (MDI) that was chain extended with either 1,4-butanediol (BD) or N-methyldiethanolamine (MDEA). The materials chain extended with MDEA were ionized using 1,3-propane sultone. The weight fraction of the hard segments was in the range 0.30–0.45. The effect of mixed soft segments, chain extenders, and zwitterionization on the extent of phase separation and physical properties was studied by utilizing differential scanning calorimetry and dynamic mechanical, stress-strain, and Fourier Transform Infrared spectroscopy experiments. All of these short segment block copolymers showed nearly complete phase separation. The zwitterionomer materials exhibited ionic aggregation within the hard domains. Although hard segment crystallinity or ionic aggregation did not affect the morphology, hard domain cohesion was important in determining the tensile and viscoelastic properties of these elastomers.     

Microstructural evolution underlying the ternary stages of the elastic behaviors for poly(ether‐b‐amide) copolymer elastomers

Three stages of elastic behavior were observed during cyclic deformations for poly(ether‐b‐amide) (PEBA) segmented copolymers based on crystalline hard segments of polyamide 12 (PA12) and amorphous soft segments of poly(tetramethylene oxide) (PTMO). The underlying microstructural evolution was characterized by a combination of in situ Fourier transform infrared spectroscopy (FTIR), wide‐angle X‐ray diffraction (WAXD), and small‐angle X‐ray scattering (SAXS) technologies. The γ–α″ phase transition of crystalline PA12 occurred upon stretching, and the orientation of the α″ phase was less reversible under larger strains. PTMO chain orientation cannot be restored to the initial state, contributing to plastic deformation. Driven by the entropy effect, the strain‐induced crystallization of PTMO can fuse during sample retarding, exerting little influence on the residual strain. For PEBA with a shore D hardness of 35 D, the long period (L) can be restored to the initial L after the sample was unloaded until system fibrillation. The tie molecules between adjacent oriented lamellae can be by drawn out high stress in a PEBA material with a shore D hardness of 40 D, and the relaxation led to a second long period. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 855–864