含嵌段共聚物“稀固体溶液”中共聚物胶束核的结晶行为

报道了含嵌段共聚物的可结晶型稀固体溶液中，不同共聚物胶束的结晶行为不同；结晶段形成胶束壳和形成胶束核，其结晶行为也相差很大。     

聚四氢呋喃-聚甲基丙烯酸甲酯两嵌段共聚物的结晶行为

报导了系列聚四氢呋喃-聚甲基丙烯酸甲酯结晶-非晶(硬段型)两嵌段共聚物的结晶行为，结果表明，其微相分离和结晶规律与文献上唯一进行过系统研究的同类嵌段共聚物(PEO－b－PS)都有较大的差别；结晶段结晶能力的大小是制约这类体系微相分离和结晶规律的一个重要因素．     

Morphology of a highly asymmetric double crystallizable poly(epsilon-caprolactone-b-ethylene oxide) block copolymer

The morphology of a highly asymmetric double crystallizable poly(epsilon-caprolactone-b-ethylene oxide) (PCL-b-PEO) block copolymer has been studied with in situ simultaneously small and wide-angle x-ray scattering as well as atomic force microscopy. The molecular masses Mn of the PCL and PEO blocks are 24,000 and 5800, respectively. X-ray scattering and rheological measurements indicate that no microphase separation occurs in the melt. Decreasing the temperature simultaneously triggers off a crystallization of PCL and microphase separation between the PCL and PEO blocks. Coupling and competition between microphase separation and crystallization results in a morphology of PEO spheres surrounded by PCL partially crystallized in lamella. Further decreasing temperature induces the crystallization of PEO spheres, which have a preferred orientation due to the confinements from hard PCL crystalline lamella and from soft amorphous PCL segments in different sides. The final morphology of this highly asymmetric block copolymer is similar to the granular morphology reported for syndiotactic polypropylene and other (co-) polymers. This implies a similar underlying mechanism of coupling and competition of various phase transitions, which is worth further exploration.     

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.     

Segmental orientation studies of polyether polyurethane block copolymers with different hard segment lengths and distributions

The orientation behavior of two series of segmented polyether polyurethanes containing different hard segment length distributions has been studied as a function of the average hard segment length which was varied from one to five methylene bis (p-phenyl isocyanate) (MDI) units. The orientation behavior of the soft segments, isolated hard segments, and of hard segments aggregated in hard domains was determined from the dichroic behavior of representative infrared bands. As the hard segment length increases, a transition in orientation behavior is observed which corresponds to a change in sample morphology.The effects of annealing and hard segment length distribution were also studied and were shown to affect the orientation response through their influence on sample morphology. Orientation hysteresis studies were performed to probe the mechanism of the transverse orientation and orientation inversion which occurred in polyurethanes with the longer, more crystallizable hard segment lengths.     

微相分离及链结构对聚酯-聚醚嵌段共聚物分子运动的影响

本文首先研究了成型方法和热处理对聚对苯二甲酸乙二酯与聚氧四亚甲基嵌段共聚物动态力学温度谱的影响,结合应力-应变曲线讨论了微相分离与力学性能的关系。其次,比较了三种不同链结构的聚酯-聚醚嵌段共聚物在不同温控程序下的动态力学温度谱,讨论了链结构对软链段结晶的影响。最后观察了聚氨酯-聚醚嵌段共聚物双重玻璃化转变现象并作了解释。     

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     

Small-angle X-ray scattering studies of microdomain structure in segmented polyurethane elastomers

The small-angle x-ray scattering (SAXS) technique has been used to characterize the detailed microphase structure of two crosslinked segmented polyurethane elastomers. Both copolymers contain trifunctional polypropylene ether triols in the rubbery elastomeric block, but are synthesized with different hard segments: a symmetric 4,4′-diphenylmethane diisocyanate (MDI) chain extended with butanediol (BD); and an 80/20 mixture of asymmetric 2,4-toluene diisocyanate (TDI) and symmetric 2,6-toluene diisocyanate (TDI) chain extended with ethylene glycol (EG). Calculations of SAXS invariants and determinations of deviations from Porod's law are used to examine the degree of phase segregation of the hard- and soft-segment domains. Results show that the overall degree of phase separation is poorer in the asymmetric TDI/EG-based copolymer than in the symmetric MDI/BD-based copolymer. Determination of diffuse phase boundary thicknesses, however, reveals that the domain boundaries are sharper in the asymmetric TDI/EG system. The contrasting morphologies found in the two systems are interpreted in terms of differences in hard-soft segment compatibility, diisocyanate symmetry, and diisocyanate length. Coupled with conformational considerations, this information is used to construct a new model for polyurethane hard-segment microdomain structure. Important features of the model are that it takes into account the effects of hard-segment sequence length distribution and allows for folding of the longer hard-segment sequences back into the hard-segment domain.     

Reentrant morphological transitions in copolymer micelles with pH-sensitive corona

In contrast to self-assembled aggregates of conventional ionic (including polymeric) surfactants the equilibrium micelles of diblock copolymer with a pH-sensitive polyelectrolyte block can exhibit two inverse sequences of morphological transitions triggered by an increase in solution salinity. The direct sequence of the sphere-cylinder-lamella transitions is similar to that for the copolymer with a strongly dissociating ionic block and occurs at a high salt concentration in solution. The abnormal reversed sequence of the lamella-cylinder-sphere transitions is predicted to occur at relatively low ionic strength in solution. The origin of the reentrant transitions is coupling between aggregation and ionization in copolymer micelles.     

PMMA—b—PTHF／PTHF共混体系中共聚物结晶能力的增强

结晶嵌段共聚物具有一般均聚物所没有的许多特殊结晶行为。虽然,人们很早就已开始对聚氧化乙烯/聚苯乙烯诸类嵌段共聚物的结晶行为进行研究,但对这类体系相分离规律及结晶行为的认识仍很不够。这主要是因为已研究的体系非常有限,此外,大都为对体系非平衡态结构的研究。所以,尽管Whitmore和Noolandi最近提出了结晶嵌段共聚物及其共混物的平衡形态理论,但缺乏实验数据与之比较。     

Synthesis of new siloxane urethane block copolymers and their properties

Siloxane urethane block copolymers were prepared with siloxanes as the soft segment. Films were cast from a variety of solvents. Solvent has an effect on the segregation of soft and hard segments. Surface studies, including ESCA, EDS, and FT-IR, show well segregated block copolymers with enhanced siloxane on the surface. DSC studies show a low mp (-44°C) for the soft segment and a T_g for the hard segment above room temperature. These materials show higher thermal stability compared to polyether urethane block copolymers. These copolymers also show relatively good resistance to exposure to oxygen plasma and show improved flame retardancy compared to nonsiliconated, polyether polyurethane block copolymers. © 1994 John Wiley & Sons, Inc.     

Gas permeation of poly(amide-6-b-ethylene oxide) copolymer

Block copolymers exhibit a different gas permeation behavior from that of homopolymers. In the diffusion process, the fraction of impermeable regions in the block copolymer decreases the diffusivity and the permeability. As the amount of impermeable regions in the block copolymer increases, the flow paths for the gas diffusion are restricted. Poly(amide-6-b-ethylene oxide) (PEBAX^®) copolymer consists of a regular linear chain of rigid polyamide for hard segment interspaced with flexible polyether for soft segment. PEBAX^® copolymer shows a typical permeation behavior of rubbery polymers. The permeability of CO₂ increases with the pressure originating from the increment of the sorbed CO₂ amounts. PEBAX^® copolymer shows the high permeability and the high selectivity for polarizable/nonpolar gas pairs. Particularly, the selectivity of CO₂ over N₂ is 61 and that of SO₂ over N₂ is 500. For small and nonpolar gases (i.e. He, H₂, O₂ and N₂), the permeability decreases with increasing the molecular size or volume of gases. On the other hand, for polarizable and larger gases (i.e. CO₂ and SO₂), it shows the high permeability. The high permeability and permselectivity of PEBAX^® copolymer are attributed of polarizable gases to polyether segment in PEBAX^®.     

Mixed Polyether-Polyester Multiblock Copolymer and its Blood Compatibility

A new type of polyether-polyester block copolymer (MPEE) consisting of two components of polyethers (PTMGT and PEGT) as soft segment and one polyester (PET) as hard segment has been synthesized. It has also been investigated in comparison with blended polyether-polyester block copolymer (BPEE) consisting of the same composition ratio of hard and soft segments and both of the two polyethers (PTMG and PEG). It was found that 1) Improvement of blood compatibility of polyether-polyester block copolymer can be achieved by introducing the hydrophilic component PEG into it; 2) generally the blood compatibility of MPEE is better than that of BPEE; 3) at a specific molar ratio of PTMGT-PET to PEGT-PET (60/40), the blended copolymer (BPEE 60/40) shows the best blood compatibility, as well as the best mechanical properties. This might be related to smaller-size microphaseseparated structures. The relationship between blood compatibility and structure of the copolymer is discussed. Polyether-polyester block copolymer containing hydrophilic and hydrophobic components might be a useful material with antithrombogenicity.     

A pH‐responsive self‐fluorescent polymeric micelle as a potential optical imaging probe

A series of methoxypolyethylene glycol‐terminated self‐fluorescent polyurethane multi‐block copolymers with excellent pH‐responsivity, self‐fluorescence, and biocompatibility are designed and synthesized. In our design, 1, 4‐bis (hydroxyethyl) piperazine is chosen as a pH‐responsive segment which can donate or accept protons in response to the change of environmental pH, and fluorescein isothiocyanate is used as a fluorescent dye conjugated into the micelles to offer self‐fluorescence. The chemical structure of the polyurethane multi‐block copolymers is characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy. The results of the acid‐based titration, the fluorescence spectrometry, and the ultraviolet visible spectroscopy indicate that the polyurethane multi‐block copolymers own an excellent pH‐buffering capacity responded to the change of pH values and the favorable self‐fluorescence property in an aqueous solution. And the ultraviolet absorption peaks of samples are strengthened with increasing of pH values, indicating that methoxypolyethylene glycol‐terminated self‐fluorescent polyurethane multi‐block copolymer can be a pH‐dependent fluorescent probe in a broad pH range. In addition, the in vitro cytotoxicity test showed that the polyurethane multi‐block copolymer has low cytotoxicity and good biocompatibility, which make it a promising nanoplatform for molecular imaging, diagnosis, and treatment of disease.     

Thermal and self-nucleation behavior of molecular complexes formed by p-nitrophenol and the poly(ethylene oxide) end block within an ABC triblock copolymer

We have been able to prepare a molecular complex between the poly(ethylene oxide) block of a poly(ethylene)-b-poly(ethylene-alt-propylene)-b-poly(ethylene oxide) triblock copolymer and p-nitrophenol (PNP). The composition of the copolymer employed was: 24% PE, 57% PEP and 19% PEO in weight percent. The pure copolymer exhibited a non-conventional thermal behavior since the PEO block displayed a fractionated crystallization process during cooling. The PEO block/PNP complex did not show any apparent crystallization during cooling, instead cold crystallization during heating was observed and an approximately 30°C increase in melting point as compared to the neat PEO block within the copolymer. This caused an overlap in the melting regions of the PE block and the PEO block/PNP complex. The self-nucleation of the PE-b-PEP-b-PEO/PNP complex is very different from that of the neat triblock copolymer. An increased capacity for self-nucleation of the PEO block was produced by the complexation with PNP and therefore the three self-nucleation domains were clearly encountered for both the PE block and for the PEO block/PNP complex. Self-nucleation was able to show that the two crystallizable blocks can be self-nucleated and annealed in an independent way, thereby ascertaining the presence of separate crystalline regions in the triblock copolymer. Through the use of PNP, both the crystallinity and the melting point of the PE-b-PEP-b-PEO block copolymer employed here can be substantially increased. Similar results were obtained by complexation of the same ABC triblock copolymer with resorcinol.     

Investigations of a series of PPDI-based polyurethane block copolymers. I. General morphology

The morphology of a series of segmented polyurethane block copolymers is characterized by x-ray scattering, differential scanning calorimetry (DSC), density measurements, and tensile studies. The materials contain hard segments formed from paraphenylene diisocyanate (PPDI) and flexible segments formed from poly(oxytetramethylene) (POTM) ranging in molecular weight from 650 to 2000. Four different molecular weight compositions were investigated, with the weight fraction of the hard segment (w_h) ranging from 0.14 to 0.33. The microphase structure has been examined using small-angle x-ray scattering, and the microphase transition zone thickness is estimated to be on the order of 1 nm. Oriented samples have been characterized with wide-angle x-ray scattering, and the flexible segment is shown to undergo stress-induced crystallization. DSC thermograms show flexible segment melting in the compositions containing the highest two molecular weights of the flexible segments. The hard segment thermal transitions were complex with a broad melting peak that varied with weight fraction and with a high temperature transition attributed to regions with hard segment lengths longer than the bulk of the hard segment component. There is an increase in tensile strength and initial modulus and decrease in elongation with increasing w_h. Density data suggest the existence of a multiphase system.     

Segmented polyurethanes with 4,4′-bis-(6-hydroxyhexoxy)biphenyl as chain extender. Part 2. Synthesis and properties of MDI-polyurethanes in comparison with 2,4-TDI-polyurethanes

Linear segmented polyurethanes based on poly(butylene adipate)s (PBA) of different molecular weight (M_n 2000, 1000, and 600), 4,4′-diphenylmethane diisocyanate (MDI) and the mesogenic diol 4,4′-bis-(6-hydroxyhexoxy)biphenyl (BHHBP) as well as the unsegmented polyurethane consisting of MDI/BHHBP units have been synthesized and characterized by elemental analysis, ¹³C-NMR and SEC. The thermal behavior and the morphology were studied by DSC, polarizing microscopy, and DMA. The properties of the MDI-polyurethanes were discussed in relation to the BHHBP chain extended 2,4-TDI-polyurethanes and common 1,4-butanediol chain-extended MDI products. MDI polyurethanes based on PBA (M_n 2000) exhibit a glass transition temperature T_g of about −40°C independent of the hard segment content up to ∼50% hard segments. At higher hard segment contents increasing T_gs were observed. Polyurethanes, based on the shorter polyester soft segments PBA (M_n 1000 or 600), reveal an increase in the glass transition temperatures with growing hard segment content. The thermal transitions caused by melting of the MDI/BHHBP hard segment domains are found at 50 K higher temperatures in comparison with the analogous TDI products with mesogenic BHHBP/TDI hard segments. Shortening of the PBA chain length causes a shift of the thermal transitions to lower temperatures. Polarizing microscopy experiments indicate that liquid crystalline behavior is influenced by both the content of mesogenic hard segments and the chain length of the polyester. © 1996 John Wiley & Sons, Inc.     

On modulating the self-assembly behaviors of poly(styrene-b-4-vinylpyridine)/octyl gallate blends in solution state via hydrogen bonding from different common solvents

We have investigated the complexation-induced phase behavior of the mixtures of poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) and octyl gallate (OG) due to hydrogen bonding in different solvents. The Fourier transform infrared spectroscopic result indicates that the hydrogen-bonding was formed between the P4VP blocks and OG in both THF and DMF, implying the P4VP blocks can bind to OG. For PS-b-P4VP/OG mixture in chloroform, the morphological transitions were induced from the unimer configuration to swollen aggregate and complex-micelles by adding OG. Interestingly, the complex-micelles can lead the formation of the honeycomb structure from chloroform solution. The PS-b-P4VP/OG mixture in THF, behaving an amphiphilic diblock copolymer in solution state, exhibited a series of morphological transitions from sphere, pearl-necklace-liked rod, worm-liked rod, vesicle, to core-shell-corona aggregates by increasing the OG content. In contrast, the PS-b-P4VP/OG mixture in DMF maintained the unimer configuration upon adding OG. Therefore, the complexation-induced morphology of the mixtures of PS-b-P4VP and OG can be mediated by adopting different common solvents to affect the self-assembly behavior.     

Nano-organization of amylose-b-polystyrene block copolymer films doped with bipyridine

This paper discusses the self-assembly of rod-coil amylose-b-polystyrene (Mal-b-PS) block copolymer thick and thin films. The nano-organization falls in an interdomain spacing d of about 10 nm, much smaller than flexible-flexible petrol block copolymer systems. Additionally, hydrogen-bonding interactions between carbohydrate rods (amylose) and 4',4-bipyridine (bipy) molecules induces phase transitions. Indeed, adding bipy in maltooctadecaose-block-polystyrene (Mal18-b-PS) copolymers results, at room temperature, in the formation of a lamellar phase having Mal18 bipy-rich nanodomains instead of hexagonal close-packed (HCP) of cylinders made of Mal18, whereas a coexistence of Mal7bipy-rich cylindrical and spherical nanodomains are formed from maltoheptaose-b-polystyrene (Mal7-b-PS) copolymers instead of a poorly organized array of Mal7-based cylinders. On heating, the Mal7bipy-b-PS system shows more rich phase behavior as compared to the Mal7-b-PS one due to weakening of hydrogen bonding with temperature. Such a system is of great interest in developing active layers in light-emitting diodes (LEDs) or in photovoltaic cells to realize devices with an optimal structure, that is, having large interface area and domain size with similar exciton diffusion length (10 nm).     

Polymerization of α,α-disubstituted-β-propiolactones and lactams. 10. Crystalline structure,thermal and mechanical studies of statistical and block copolymers of pivalolactone and α-methyl-α-propyl-β-propiolactone

AB and ABA block copolyesters based on racemic poly(α-methyl-α-n propyl-α-propiolactone) (PMPPL) as a “soft” or elastomeric segment and polypivalolactone (PPL) as a “hard” or crystallizable segment have been synthesized and compared with random copolymers of the same composition. X-ray studies show the coexistence of polymorphic crystal forms for a given polymer in a given sample. Thermal and dynamic mechanical properties give clear evidence of heterophase structure corresponding to segregation of PPL and PMPPL. The crystalline phase clearly provides thermally reversible crosslinking in the ABA block copolymers. On stretching, the planar zigzag form of PMPPL is observed. Because of the domain structure, moduli of ABA samples are higher than those of PMPPL and their tensile strengths are similar to those of comparable styrene-butadiene block copolymers. The polymer synthesis was achieved by sequential monomer addition with tetrahexyl ammonium benzoate as initiator. For the ABA polymers the diammonium salt of sebacic acid provided a di-functional initiator. The agreement between calculated and observed molecular weights testify to the “living” character of this polymerization reaction.