Block copolyesters of poly(pentamethylene p,p′‐bibenzoate) and poly(tetramethylene adipate)

Hydroxy‐terminated poly(pentamethylene p,p′‐bibenzoate) oligomers with different molecular weights were prepared. The poly(pentamethylene p,p′‐bibenzoate) oligomers showed rather high crystallinity, and some of them exhibited a monotropic smectic phase. Block copolyesters with hard segments of poly(pentamethylene p,p′‐bibenzoate) and soft segments of poly(tetramethylene adipate) were prepared by coupling the poly(pentamethylene p,p′‐bibenzoate) oligomer and a poly(tetramethylene adipate)glycol with methylene‐4,4′‐diphenylene diisocyanate in solution. The block copolyesters were characterized by IR, ¹H NMR, differential scanning calorimetry, a polarized microscope, and X‐ray diffraction. The thermal transitions of the block copolyesters were dependent on the composition and the molecular weight of the poly(pentamethylene p,p′‐bibenzoate) oligomer used. The hard segments in the block copolyesters showed no liquid crystallinity and exhibited rather low crystallinity or were even amorphous. The molecular weight of the poly(pentamethylene p,p′‐bibenzoate) oligomer used influences the glass‐transition temperature and crystalline properties of the soft segments in the block copolyesters significantly. The effect on the glass‐transition temperature of the soft segments is described as the difference in miscibility between the hard and soft segments. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2626–2636, 2002     

Melt transesterification and characterization of segmented block copolyesters containing 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol

Conventional melt transesterification successfully produced high‐molecular‐weight segmented copolyesters. A rigid, high‐T_g polyester precursor containing the cycloaliphatic monomers, 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol, and dimethyl‐1,4‐cyclohexane dicarboxylate allowed molecular weight control and hydroxyl difunctionality through monomer stoichiometric imbalance in the presence of a tin catalyst. Subsequent polymerization of a 4000 g/mol polyol with monomers comprising the low‐T_g block yielded high‐molecular‐weight polymers that exhibited enhanced mechanical properties compared to a nonsegmented copolyester controls and soft segment homopolymers. Reaction between the polyester polyol precursor and a primary or secondary alcohol at melt polymerization temperatures revealed reduced transesterification of the polyester hard segment because of enhanced steric hindrance adjacent to the ester linkages. Differential scanning calorimetry, dynamic mechanical analysis, and tensile testing of the copolyesters supported the formation of a segmented multiblock architecture. Further investigations with atomic force microscopy uncovered unique needle‐like, interconnected, microphase separated surface morphologies. Small‐angle X‐ray scattering confirmed the presence of microphase separation in the segmented copolyesters bulk morphology. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Novel copolyesters based on poly(alkylene dicarboxylate)s: 2. Thermal behavior and biodegradation of fully aliphatic random copolymers containing 1,4-cyclohexylene rings

Aliphatic poly(butylene 1,12-dodecanedioate) is an interesting biodegradable polyester characterized by high thermal stability and high crystallinity, but low melting temperature. In order to improve the performances of this polymer some novel fully aliphatic random copolyesters have been prepared starting from 1,4-butanediol and different molar ratio of 1,12-dodecanedioc acid and 1,4-cyclohexanedicarboxylic acid. The copolymers have a notable resistance to thermal degradation, thermal properties which vary as a function of the composition, and maintain the mechanical characteristics of the poly(alkylene dicarboxylate). In particular, the copolymer containing the 70 mol% of 1,4-cyclohexanedicarboxylate units improves the thermal properties of the poly(butylene 1,12-dodecanedioate) and presents a very high biodegradation rate, higher than those of the two parent homopolymers. This behavior has been correlated to the low level of crystallinity of the sample and to the composition of the amorphous phase. Therefore, these novel fully aliphatic copolymers represent an interesting new class of copolyesters which can balance good physical properties and high biodegradability.     

Novel poly(butylene succinate-co-lactic acid) copolyesters: Synthesis, crystallization, and enzymatic degradation

A series of aliphatic biodegradable poly(butylene succinate-co-dl-lactide) (PBSLA) copolyesters were synthesized with the aim of improving the degradation rate of poly(butylene succinate) (PBS) by incorporation of dl-oligo(lactic acid) (OLA) into the PBS molecular chains. The composition and sequential structure of the aliphatic copolyesters were investigated by proton nuclear magnetic resonance (¹H NMR) spectroscopy. The crystallization behaviors, the crystal structure and morphology of the copolyesters were investigated by using differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and polarizing optical microscopy (POM), respectively. The results indicate that the crystallization of the copolyesters was restricted by the incorporation of lactide (LA) units, which further tuned the mechanical properties of the copolyesters. The copolyesters could form complete spherulites and exhibit the same crystal structure as that of PBS. Enzymatic study indicated that the copolyesters with higher content of LA units degraded faster, and the degradation began in the amorphous regions and then in the crystalline regions. The morphology and the resulting degradation products of the copolyesters were investigated by scanning electron microscopy (SEM) and ¹H NMR analysis during the degradation process.     

Novel biodegradable copolyesters containing blocks of poly(3-hydroxyoctanoate) and poly(epsilon-caprolactone): synthesis and characterization

Novel biodegradable polyester block copolymers have been synthesized by using well-defined poly(3-hydroxyoctanoate) (PHO) oligomers having a hydroxyl end group and an ester end group with M(n) values of 800, 2,500, 5,300, 8,000, or 20,000 as an elastomeric soft segment and poly(epsilon-caprolactone) as a more crystalline segment. These PHO oligomers prepared by methanolysis were subjected to block copolymerization with epsilon-caprolactone. The chemical structure of the copolymers was confirmed by (1)H NMR and (13)C NMR spectroscopy. All the copolyesters are semi-crystalline and two T(g) were observed by differential scanning calorimetry when the molecular weight of the PHO block is about 20,000.     

Degradation of cross-linked aliphatic polyester composed of poly(?-caprolactone-co-d,l-lactide) depending on the thermal properties

In this study, we prepared cross-linked aliphatic polyester derived from branched poly(?-caprolactone (abbreviated as CL)-co-d,l-lactide (abbreviated as LA)) macromonomers with different CL and LA compositions and investigated the effect of thermal properties on their degradation. According to the degradation study, the weight loss became larger with increasing LA composition in poly(CL-co-LA). The introduction of LA units that can degrade easily disturbed the crystallinity of the PCL segments; as result, the hydrolysis became accelerated. Also, we studied the temperature dependency of degradation of a series of cross-linked poly(CL-co-LA) materials with different melting points. We found that the degradation of these materials related closely to the crystallinity, which could be controlled by the composition of CL and LA.     

Polyurethane elastomers with hydrolytic and thermooxidative stability. I. Polyurethanes with N-alkylated polyamide soft blocks

Segmented polyurethanes with N-alkylated amides as soft blocks as prepared. Comparisons are made with both a poly(ester urethane) and a poly(ether urethane) with the same hard block; the poly(amide urethane) is more hydrolytically stable than the polyester containing material and demonstrates greater thermooxidative stability than that with the polyether moiety. The aliphatic poly(amide urethane)s remain transparent upon exposure to uv light.     

Copolyesteramides—III. Anionic copolymers of ε-caprolactam with ε-caprolactone. Crystalline character and mechanical properties

The crystalline character of anionic copolymers of ε-caprolactam with ε-caprolactone and of some alternatingly-sequenced analogues has been studied and investigations made of the mechanical and dynamic mechanical properties of the anionic copolymers. The anionic copolymers are crystalline over the whole range of compositions. Depending on the proportions of NH(CH₂)₅CO and O(CH₂)₅CO units and the thermal history of the copolymers, the crystalline phases present are either wholly of polyamide type or composed of co-existing and mutually incompatible polyamide and polyester entities. However, the constituents appear to be miscible in the amorphous phase. The mechanical properties of the copolymers (like their crystalline melting temperatures) change discontinuously with composition, showing minima in the values of initial modulus, yield stress and breaking stress at ca 25–40% amide-group content where dual crystallinity exists. In addition to their variation with composition, the properties are also affected by changes in the procedure of anionic copolymerisation.     

对苯二甲酸丁二酯-ε-己内酯多嵌段共聚物中硬链段的受限结晶

用差示扫描量热法（DSC）,广角X射线衍射（WAXD）,傅立叶变换红外光谱（FTIR）等技术研究了对苯二甲酸丁二酯-ε-己内酯（PBT—PCL）多嵌段共聚物中硬链段的受限结晶。结果表明,PBT—PCL共聚酯中软硬链段在非晶区的混容性比较好,不同组成的样品均显示出一个玻璃化转变温度;对硬段含量超过50%的共聚酯来说,硬链段可以结晶,而软链段不能结晶;由于硬链段的受限特点,BT硬链段的结晶受软链段的影响和制约,其结晶能力随硬段序列长度的增加而逐渐增大。     

不饱和聚酯／聚氨酯复合体系的研究

以端羟基不饱和聚酯（ＨＵＰ）与聚氨酯（ＰＵ）浇注型复合网络聚合物（ＣＰＮｓ）为基材，考察了化学动力学及相分离对ＣＰＮ聚合物物理机械性能的影响．数据揭示了不饱和聚酯／聚附聚氨酯（ＨＵＰ／ＰＵ－ｅｓ）ＣＰＮ，当ｒ＝ＮＣＯ／ＯＨ＝０．４时，它的物理力学性能优于不饱和聚酯／聚醚聚氨酯（ＨＵＰ／ＰＵ－ｅｔ）ＣＰＮ或ＨＵＰ／ＰＡＰＩＣＰＮ组成物．最佳ＣＰＮ可通过调整聚氨酯中软段和硬段组分及网络组成而设计与制备．     

含有二个聚醚软链段的聚醚聚酯嵌段共聚物的合成及其血液相容性的研究

本文报道了一类新的具有二种聚醚软链段(PTMGT和PEGT)和一种聚酯硬链段(PET)的混合聚醚-聚酯嵌段共聚物(MPEE)的合成和它的血液相容性,并与具有相同软、硬链段比及相同软链段组成比(PTMGT/PEGT)的二种聚醚聚酯嵌段共聚物(PTMGT-PET和PEGT-PET)的共混物(BPEE)的性质进行了比较,结果表明:(1)聚醚聚酯嵌段共聚物的血液相容性可以通过引入亲水性好的PEGT组分而得到提高;(2)在多数的组成比下,共聚型的MPEE具有比共混型的BPEE优良的血液相容性;(3)特定的组成比:PTMGT/PEGT=60/40(mol),共混型的BPEE:(60/40)呈现最好的血液相容性以及最佳的力学性质。研究中发现材料的微相分离结构同血液相容性有关,细微的相分离结构可导致优良的血液相容性。     

A Molecular Dynamics Simulation on the Self‐Assembly of ABC Triblock Copolymers, 1. Effects of Block Composition in Symmetric Triblock Copolymers

The self‐assembly of ABC triblock copolymers in the microphase‐separated state is investigated using an isothermal‐isobaric molecular dynamics simulation. For the validation of our simulation scheme, ABA triblock copolymers are also simulated. We examine the effect of the composition (f_B) of symmetric triblock copolymers on the morphology realized in these copolymers, keeping other parameters fixed. For ABA triblock copolymers, the transition from lamellar to cylindrical morphologies is observed with increasing the composition from f_B = 0.5 to f_B = 0.75, and such behavior is supported by calculation results of scattering patterns. These simulated results agree well with experimental and theoretical ones, validating our simulation method. More complex structures are predicted for ABC triblock copolymers. If midblock B is the minor component, its structures are changed from lamellar, cylindrical, to spherical morphology at the interface between A/C lamellae as f_B decreases. For ABC triblock copolymers with the midblock B as the major component, the morphology of end blocks in the matrix composed of the midblock is changed from tricontinuous to spherical structures as f_B increases.     

Sequential and localized grafting on aliphatic polyester diblock copolymers using alkyne deprotection and click cycloaddition

Diblock copolymers, in which both blocks are composed of aliphatic polyesters, were synthesized from two different alkyne‐functionalized δ‐valerolactone monomers by ring opening polymerization and subsequent click cycloaddition. Trimethylsilyl protection of the alkyne functionality of one block was instrumental to the success of the synthesis. These novel aliphatic polyester diblock copolymers were characterized by ¹H and ¹³C NMR spectroscopy, gel permeation chromatography (GPC), and infrared (IR) spectroscopy. Sequential functionalization of the diblock copolymers with hydrophobic groups on one block, and hydrophilic groups on the other block, provides access to amphiphilic structures. Micellar structures generated from these polyester amphiphiles were characterized by fluorescence spectroscopy and transition electron microscopy (TEM). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Supramolecular structures from self-assembled poly(γ-benzyl-l-glutamate)-polydimethylsiloxane-poly(γ-benzyl-l-glutamate) triblock copolypeptides in thin films

We describe the self-assembly of A-B-A triblock copolymers in thin films composed of a soft polydimethylsiloxane (PDMS) central block (B) and two polypeptidic (A) blocks, poly(γ-benzyl)-l-glutamate (PBLG). The PBLG segment exhibits depending on the chain length two distinct secondary conformations either a β-sheet or a α-helical conformation. The direct relationship between the surface morphology and the secondary conformation of the polypeptide segment has been evidenced by atomic force microscopy. For chain lengths below 20 U the polypeptide segments adopt preferentially a β-sheet secondary structure and the triblock copolymer self-assembled in fibers. Moreover, the fiber diameters increased with the chain length of the triblock copolymer. For chain lengths above 20, the α-helical structure is stabilized and a lamellar morphology is formed driven by rod-rod interactions in spite of the very asymmetric composition of the triblock copolymer. However, decreasing the film thickness from 25 to 8 nm, i.e., below the L/2 and due to the preferential attraction of the polypeptide block for the hydrophilic substrate employed, instead of a lamellar morphology a rod-like morphology could be found. Thus, the use of hybrid block copolymer containing polypeptides with particular secondary structures offers novel alternatives to control the self-assembly in thin films compared to traditional amorphous block copolymers.     

STUDIES ON THERMOTROPIC LIQUID CRYSTALLINE COPOLYESTERS:POLY (ARYLENE TEREPHTHALATECO-HEXAMETHYLENE TEREFHTHALATE)

A series of copolyesters based on terephthaloyl chloride, hexamethylene glycol and hydroquinone or chlorohydroquinone were prepared. The copolymers showed composition-dependent liquid crystalline properties as verified by visual observation of stir-opalescence, polarizing microscope and DSC. The copolyesters with aromatic diol contents over a certain extent (x≥0.2) were thermotropic with wide liquid crystalline temperature ranges. Comparing with the copolyesters based on butylene glycol or ethylene glycol, the minimum fraction of aromatic diol (x value) used to get the liquid crystallinity for all these copolyesters is around 0.2 regardless of the chain lengths of aliphatic glycols. ~1H-NMP studies revealed that copolyesters have microstructure of block sequence distribution and the mesogenie segments shorter than triad with three phenyl nuclei will not provide the liquid crystallinity.     

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.     

液晶聚酯与环氧嵌段共聚物的合成及表征

近年来 ,人们利用高分子液晶作为热固性环氧树脂的改性剂 ,不仅可以提高环氧树脂的韧性和强度 ,而且可以改善其热性能 ,为制备高性能的环氧树脂提供了一条新的途径[1,2 ] .目前报道所使用的液晶聚合物大多为液晶聚酯[3 ] 或液晶性聚氨酯[4] ,这些液晶聚合物与环氧树脂由于存在相容性不好的问题 ,给其实际应用带来了困难 .为了改善二者的相容性 ,本文采用溶液法合成了末端带有反应活性基团的聚酯型液晶聚合物 ,将它再与双酚Ａ环氧预聚物反应 ,制得了高分子液晶环氧嵌段共聚物 ,其合成路线如下 :2ＨＯＣＯＯＣＨ3+ ＨＯ(ＣＨ2 ) 6 ＯＨ　　Ｈ…     

Synthesis, characterization and properties of high molecular weight poly(butylenes succinate) reinforced by mesogenic units

To increase the molecular weights of the synthesized liquid crystalline aromatic/aliphatic copolyesters and to avoid crosslinking, a solution polymerization of the prepolymer and chain extender hexamethylene diisocyanate was adopted. The effects of chain extension on polyester molecular weights, thermal and mechanical properties, and biodegradable behaviors were investigated respectively. The catalysis mechanism and the copolyesters morphological textures were also investigated. The synthesized copolyesters were characterized by means of Fourier transform infrared spectra (FTIR), gel permeation chromatography (GPC), viscosity measurements, differential scanning calorimetry (DSC), X-ray diffraction (XRD), polarizing light microscopy (PLM), scanning electron microscopy (SEM) and mechanical property measurements. It was found that inherent viscosities and the molecular weights of the copolyesters were remarkably increased under the action of catalyst, leading to a increase in the tensile strength. The degree of relative crystallinity, the melting temperature, and the rate of degradation decreased after chain extension.     

Syntheses and properties of ABA,CBA, and CBC triblock copolymers based thermoplastic elastomers with glassy (A), elastomeric (B), and crystalline (C) blocks

In this contribution, we describe the syntheses, characterization, and properties of ABA, CBA and CBC triblock copolymers with glassy (A), elastomeric (B), and crystalline (C) blocks. These three hard-soft-hard triblock copolymers were prepared via living ring-opening metathesis copolymerization by use of Grubbs third generation catalyst through one-pot sequential monomer addition and subsequent hydrogenation. These hard-soft-hard triblock copolymers based thermoplastic elastomers have been analyzed by proton NMR, differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), IR, and transmission electron microscopy (TEM). The mechanical properties of these triblock copolymers were also measured by monotonic and step cyclic tensile test. Compared with the ABA triblock copolymer, the CBC triblock copolymer containing highly crystalline hard end-blocks shows enhanced tensile strength and the best elastic recovery of 90.8%. The hybrid CBA triblock copolymer displays much improved elongation, which is almost twice as long as the other two TPEs, and excellent elastic recovery of 87.0%.     

Synthesis and characterization of biodegradable aliphatic copolyesters with poly(ethylene oxide) soft segments

A series of multiblock poly(ether-ester)s based on poly(butylene succinate) (PBS) as the hard segments and hydrophilic poly(ethylene oxide) (PEO) as the soft segments was synthesized with the aim of developing degradable polymers which could combine the mechanical properties of high performance elastomers with those of flexible plastics. The aliphatic poly(ether-ester)s were synthesized by the catalyzed two-step transesterification reaction of dimethyl succinate, 1,4-butanediol and α,ω-hydroxyl terminated poly(ethylene oxide) (PEO, = 1000 g/mol) in bulk. The content of soft PEO segments in the polymer chains was varied from about 10 to 50 mass%. The effect of the introduction of the soft PEO segments on the structure, thermal and physical properties, as well as on the biodegradation properties was investigated. The composition and structure of these aliphatic segmented copolyesters were determined by ¹H NMR spectroscopy. The molecular weights of the polyesters were verified by gel permeation chromatography (GPC), as well as by viscometry of dilute solutions and polymer melts. The thermal properties were investigated using differential scanning calorimetry (DSC). The degree of crystallinity was determined by means of DSC and wide-angle X-ray scattering. A depression of melting temperature and a reduction of crystallinity of the hard segments with increasing content of PEO segments were observed. Biodegradation of the synthesized copolyesters, estimated in enzymatic degradation tests in phosphate buffer solution with Candida rugosa lipase at 37 °C was compared with hydrolytic degradation in the buffer solution. The weight losses of the samples were in the range from 2 to 10 mass%. GPC analysis confirmed that there were significant changes in molecular weight of copolyesters with higher content of PEO segments, up to 40% of initial values. This leads to conclusion that degradation mechanism of the poly(ether-ester)s based on PEO segments occurs through bulk degradation in addition to surface erosion.