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1.
M. Jayakannan S. Ramakrishnan 《Journal of polymer science. Part A, Polymer chemistry》2000,38(1):261-268
Poly(4‐ethyleneoxy benzoate) (PEOB) was synthesized by the self‐condensation of ethyl 4‐(2‐hydroxyethoxy) benzoate (E4HEB) under transesterification conditions. Branched PEOB was prepared by the condensation of E4HEB with an AB2 monomer, ethyl 3,5‐bis(2‐hydroxyethoxy) benzoate (EBHEB), under similar conditions. Varying amounts of branching (0–50%) were introduced into the linear polymer by changes in the composition of the comonomers in the feed. The solution viscosity of the polymers indicated that they had reasonable molecular weights; the extent of branching in these copolymers was established from their 1H NMR spectra. Differential scanning calorimetry studies indicated that, as expected, the introduction of branching drastically affected the percent crystallinity of the copolymers (as seen from their ΔHm, the enthalpy of melting), and when the extent of the incorporation of the AB2 monomer exceeded 10 mol %, the copolymers were completely amorphous. The melting temperatures of the copolymers decreased with an increase in the branching content, whereas the peak crystallization temperature in quenched (amorphous) samples followed the exactly opposite trend. The glass‐transition temperatures (Tg) of the branched copolymers first decreased at low extents of branching, passed through a minimum, and then increased to attain the Tg of the pure hyperbranched polymer of EBHEB. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 261–268, 2000 相似文献
2.
M. A. G. Jansen L. H. Wu J. G. P. Goossens G. DE Wit C. Bailly C. E. Koning 《Journal of polymer science. Part A, Polymer chemistry》2007,45(5):882-899
To increase the Tg in combination with a retained crystallization rate, bis(2‐hydroxyethyl)terephthalate (BHET) was incorporated into poly(butylene terephthalate) (PBT) via solid‐state copolymerization (SSP). The incorporated BHET fraction depends on the miscibility of BHET in the amorphous phase of PBT prior to SSP. DSC measurements showed that BHET is only partially miscible. During SSP, the miscible BHET fraction reacts via transesterification reactions with the mobile amorphous PBT segments. The immiscible BHET fraction reacts by self‐condensation, resulting in the formation of poly(ethylene terephthalate) (PET) homopolymer. 1H‐NMR sequence distribution analysis showed that self‐condensation of BHET proceeded faster than the transesterification with PBT. SAXS measurements showed an increase in the long period with increasing fraction BHET present in the mixtures used for SSP followed by a decrease due to the formation of small PET crystals. DSC confirmed the presence of separate PET crystals. Furthermore, the incorporation of BHET via SSP resulted in PBT‐PET copolymers with an increased Tg compared to PBT. However, these copolymers showed a poorer crystallization behavior. The modified copolymer chain segments are apparently fully miscible with the unmodified PBT chains in the molten state. Consequently, the crystal growth process is retarded resulting in a decreased crystallization rate and crystallinity. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 882–899, 2007. 相似文献
3.
M. Vannini L. Finelli N. Lotti M. Colonna C. Lorenzetti A. Munari 《Journal of Polymer Science.Polymer Physics》2005,43(12):1441-1454
The thermal behavior of poly(ethylene‐co‐2,2‐bis[4‐(ethylenoxy)‐1,4‐phenylene]propane terephthalate) (PET/BHEEBT) copolymers was investigated by thermogravimetric analysis and differential scanning calorimetry. A good thermal stability was found for all the samples. The thermal analysis carried out using DSC technique showed that the Tm of the copolymers decreased with increasing BHEEBT unit content, differently from Tg, which on the contrary increased. Wide‐angle X‐ray diffraction measurements permitted identifying the kind of crystalline structure of PET in all the semicrystalline samples. The multiple endotherms similar to PET were also evidenced in the PET/BHEEBT samples, due to melting and recrystallization processes. By applying the Hoffman–Weeks' method, the Tm° of PET and its copolymers was derived. The isothermal crystallization kinetics was analyzed according to Avrami's treatment and values of the exponent n close to 3 were obtained, independently of Tc and composition. Moreover, the introduction of BHEEBT units was found to decrease PET crystallization rate. Lastly, the presence of a crystal‐amorphous interphase was evidenced. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1441–1454, 2005 相似文献
4.
The melt crystallization behaviors and crystalline structures of poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate), and poly(ethylene‐co‐trimethylene terephthalate) (PETT) were investigated with differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X‐ray diffraction at various crystallization temperatures (Tcs). The PETT copolymers were synthesized via the polycondensation of terephthalate with ethylene glycol and trimethylene glycol (TG) in various compositions. The copolymers with 69.0 mol % or more TG or 31.0 mol % or less TG were crystallizable, but the other copolymers containing 34–56 mol % TG were amorphous. The DSC isothermal results revealed that the addition of a small amount of flexible TG (up to 21 mol %) to the PET structure slightly reduced the formation of three‐dimensional spherulites. A greater TG concentration (91–100%) in the copolyesters changed the crystal growth from two‐dimensional to three‐dimensional. The DSC heating scans after the completion of isothermal crystallization at various Tcs showed three melting endotherms for PET, PETT‐88, PETT‐84, and PETT‐79 and four melting endotherms for PETT‐9 and PETT. The presence of an additional melting endotherm could be attributed to the melting of thinner and imperfect copolyester crystallites. Analyses of the Lauritzen–Hoffman equation demonstrated that PETT‐88 had the highest values of the product of the lateral and folding surface free energies, and this suggested that the addition of small amounts of flexible trimethylene terephthalate segments to PET disturbed chain regularity, thus increasing molecular chain mobility. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4255–4271, 2004 相似文献
5.
Francisco Gmez Robert Quintana Antxon Martez De Ilarduya Elisabet Rud Sebastin Muoz‐Guerra 《Journal of polymer science. Part A, Polymer chemistry》2005,43(1):92-100
A series of poly(butylene terephthalate) copolyesters containing 5‐tert‐butyl isophthalate units up to 50 mol %, as well as the homopolyester entirely made of these units, were prepared by polycondensation from a melt. The microstructure of the copolymers was determined by NMR to be random for the whole range of compositions. The effect exerted by the 5‐tert‐butyl isophthalate units on thermal, tensile, and gas transport properties was evaluated. Both the melting temperature (Tm) and crystallinity were found to decrease steadily with copolymerization, whereas the glass‐transition temperature (Tg) increased and the polyesters became more brittle. Permeability and solubility slightly increased with the content in substituted isophthalic units, whereas the diffusion coefficient remained practically constant. For the homopolyester poly(5‐tert‐butyl isophthalate), all these properties were found to deviate significantly from the general trend displayed by copolyesters, suggesting that a different structure in the solid state is likely adopted in this case. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 92–100, 2005 相似文献
6.
Munehisa Yasuniwa Shinsuke Tsubakihara Takahiro Murakami 《Journal of Polymer Science.Polymer Physics》2000,38(1):262-272
Pressure effect on the melting behavior of poly(butylene terephthalate) (PBT) and poly(hexamethylene terephthalate) (PHT) was studied by high‐pressure DTA (HP‐DTA) up to 320 and 530 MPa, respectively. Cooling rate dependence on the DSC melting curves of the samples cooled from the melt was shown at atmospheric pressure. Stable and metastable samples were prepared by cooling from the melt at low and normal cooling rates, respectively. DTA melting curves for the stable samples showed a single peak, and the peak profile did not change up to high pressure. Phase diagrams for PBT and PHT were newly determined. Fitting curves of melting temperature (Tm) versus pressure expressed by quadratic equation were obtained. Pressure coefficients of Tm at atmospheric pressure, dTm/dp, of PBT and PHT were 37 and 33 K/100 MPa, respectively. HP‐DTA curves of the metastable PBT showed double melting peaks up to about 70 MPa. In contrast, PHT showed them over the whole pressure region. HP‐DTA of stable poly(ethylene terephthalate) (PET) was also carried out up to 200 MPa, and the phase diagram for PET was determined. dTm/dp for PET was 49 K/100 MPa. dTm/dp increased linearly with reciprocal number of ethylene unit. The decrease of dTm/dp for poly(alkylene terephthalate) with increasing a segmental fraction of an alkyl group in a whole molecule is explained by the increase of entropy of fusion. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 262–272, 2000 相似文献
7.
Sang Soon Park Seung Hun Chae Seung Soon Im 《Journal of polymer science. Part A, Polymer chemistry》1998,36(1):147-156
The block copolymers of poly(butylene succinate) (PBS) and poly(butylene terephthalate) (PBT) were synthesized by melt processing for different times. The sequence distribution, thermal properties, and crystallization behavior were investigated over a wide range of compositions. For PBS/PBT block copolymers it was confirmed by statistical analysis from 1H-NMR data that the degree of randomness (B) was below 1. The melting peak (Tm) gradually moved to lower temperature with increasing melt processing time. It can be seen that the transesterification between PBS and PBT leads to a random copolymer. From the X-ray diffraction diagrams, only the crystal structure of PBS appeared in the M1 copolymer (PBS 80 wt %) and that of PBT appeared in the M3 (PBS 50 wt %) to M5 (PBS 20 wt %) copolymers. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 147–156, 1998 相似文献
8.
M. Soccio N. Lotti L. Finelli A. Munari 《Journal of Polymer Science.Polymer Physics》2008,46(8):818-830
The melting behavior and the crystallization kinetics of random poly(propylene/neopenthyl terephthalate) copolymers (PPT‐PNT) were investigated by means of differential scanning calorimetry and hot‐stage optical microscopy. Multiple endotherms were evidenced in the PPT‐PNT samples, due to melting and recrystallization processes, similarly to PPT. By applying the Hoffman‐Weeks' method, the Tm° of the copolymers was derived. Baur's equation described well the Tm‐composition data. The isothermal crystallization kinetics was analyzed according to the Avrami's treatment. The introduction of NT units decreased the crystallization rate in comparison to pure PPT. Values of the Avrami's exponent close to three were obtained in all cases, regardless of Tc, in agreement with a crystallization process originating from predeterminated nuclei and characterized by three dimensional spherulitic growth. As a matter of fact, space‐filling spherulites were observed by optical microscopy at all Tcs. Banded spherulites were found for PPT‐PNT5 and PPT‐PNT10, the band spacing being affected by both Tc and composition. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 818–830, 2008 相似文献
9.
Jun Xiao Xinhua Wan Dong Zhang Qi‐Feng Zhou S. Richard Turner 《Journal of polymer science. Part A, Polymer chemistry》2001,39(3):408-415
Copoly(ethylene terephthalate‐imide)s (PETIs) were synthesized by the melt copolycondensation of bis(2‐hydroxyethyl)terephthalate with a new imide monomer, N,N′‐bis[p‐(2‐hydroxyethoxycarbonyl)phenyl]‐biphenyl‐3,3′,4,4′‐tetracarboxydiimide (BHEI). The copolymers were characterized by intrinsic viscosity, Fourier transform infrared, 1H NMR, differential scanning calorimetry, and thermogravimetric analysis techniques. Although their crystallinities decreased as the content of BHEI units increased, the glass‐transition temperatures (Tg) increased significantly. When 5 or 10 mol % BHEI units were incorporated into poly(ethylene terephthalate), Tg increased by 10 or 24 °C, respectively. The thermal stabilities of PETI copolymers were about the same as the thermal stability of PET, whereas the weight loss of PETIs decreased as the content of BHEI units increased. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 408–415, 2001 相似文献
10.
M. Soccio N. Lotti L. Finelli M. Gazzano A. Munari 《Journal of Polymer Science.Polymer Physics》2008,46(2):170-181
Poly(propylene/neopenthyl terephthalate) random copolymers (PPT‐PNT) and poly(neopenthyl terephthalate) (PNT) were synthesized and subjected to molecular characterization. Afterwards, the polyesters were examined by TGA, DSC, andX‐ray. The copolymers, which displayed a good thermal stability, at room temperature appeared as semicrystalline materials: the main effect of copolymerization was a lowering in the amount of crystallinity and a decrease of the melting temperature with respect to homopolymer PPT. XRD measurements allowed the identification of the PPT crystalline structure in all cases. Amorphous samples were obtained after melt quenching, with the exception of PPT‐PNT5, and an increment of Tg as the content of NT units is increased was observed due to the effect of the side methylene groups in the polymeric chain. The Wood equation described well Tg‐composition data. Lastly, the presence of a rigid‐amorphous phase was evidenced in the copolymers, whose amount depended on composition and on thermal treatment. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 170–181, 2008 相似文献
11.
Cuiqing Teng Kai Yang Ping Ji Muhuo Yu 《Journal of polymer science. Part A, Polymer chemistry》2004,42(20):5045-5053
An Erratum has been published for this article in J. Polym. Sci. Part A: Polym. Chem. (2004) 42(22) 5845 New multiblock copolymers derived from poly(L‐lactic acid) (PLLA) and poly(ε‐caprolactone) (PCL) were prepared with the coupling reaction between PLLA and PCL oligomers with ? NCO terminals. Fourier transform infrared (FTIR), 13C NMR, and differential scanning calorimetry (DSC) were used to characterize the copolymers and the results showed that PLLA and PCL were coupled by the reaction between ? NCO groups at the end of the PCL and ? OH (or ? COOH) groups at the end of the PLLA. DSC data indicated that the different compositions of PLLA and PCL had an influence on the thermal and crystallization properties including the glass‐transition temperature (Tg), melting temperature (TM), crystallizing temperature (Tc), melting enthalpy (ΔHm), crystallizing enthalpy (ΔHc), and crystallinity. Gel permeation chromatography (GPC) was employed to study the effect of the composition of PLLA and PCL and reaction time on the molecular weight and the molecular weight distribution of the copolymers. The weight‐average molecular weight of PLLA–PCL multiblock copolymers was up to 180,000 at a composition of 60% PLLA and 40% PCL, whereas that of the homopolymer of PLLA was only 14,000. A polarized optical microscope was used to observe the crystalline morphology of copolymers; the results showed that all polymers exhibited a spherulitic morphology. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5045–5053, 2004 相似文献
12.
Valentina Siracusa Massimo Gazzano Lara Finelli Nadia Lotti Andrea Munari 《Journal of Polymer Science.Polymer Physics》2006,44(11):1562-1571
Poly(diethylene terephthalate‐co‐thiodiethylene terephthalate) (PDET/TDET) copolymers of various compositions were synthesized and characterized in terms of chemical structure and molecular weight. The thermal behavior was examined by thermogravimetric analysis and differential scanning calorimetry. All the polymers showed a good thermal stability. At room temperature they appeared as semicrystalline materials: the main effect of copolymerization was a lowering in the amount of crystallinity and a decrease of melting temperature with respect to homopolymers. WAXD measurements indicated that cocrystallization occurs over an extended composition range and three different crystalline phases have been identified. In particular, the applicability of Wendling–Suter's equation has been checked for the PDET/TDET copolymers with TDET unit content ranging from 60 to 90 mol %. Amorphous samples were obtained after melt quenching and a decrease of Tg as the content of TDET units is increased was observed. This behavior was explained as due to the presence of flexible C? S? C bonds in the polymeric chain. Lastly, the Fox equation well described Tg‐composition data. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1562–1571, 2006 相似文献
13.
Tzong‐Ming Wu Chi‐Chin Chang T. Leon Yu 《Journal of Polymer Science.Polymer Physics》2000,38(19):2515-2524
Melt crystallization behaviors of poly(ethylene terephthalate) (PET) and poly(ethylene terephthalate‐co‐isophthalate) (PETI) containing 2 and 12 mol % of noncrystallizable isophthalate components were investigated. Differential scanning calorimetry (DSC) isothermal results revealed that the introduction of 2 mol % isophthalate into PET caused a change of the crystal growth process from a two‐dimensional to a three‐dimensional spherulitic growth. The addition of more isophthalate up to 12 mol % into the PET structure induced a change in the crystal growth from a three‐dimensional to a two‐dimensional crystal growth. DSC heating scans after completion of isothermal crystallization at various Tc's showed three melting endotherms for PET and four melting endotherms for PETI‐2 and PETI‐12. The presence of an additional melting endotherm is attributed to the melting of copolyester crystallite composed of ethylene glycol, tere‐phthalate, and isophthalate (IPA) or the melting of molecular chains near IPA formed by melting the secondary crystallite Tm (I) and then recrystallizing during heating. Analyses of both Avrami and Lauritzen‐Hoffman equations revealed that PETI containing 2 mol % of isophthalate had the highest Avrami exponent n, growth rate constant Go, and product of lateral and end surface free energies σσe. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2515–2524, 2000 相似文献
14.
Ji‐Xing Yang Jing Cui Ying‐Yun Long Yan‐Guo Li Yue‐Sheng Li 《Journal of polymer science. Part A, Polymer chemistry》2014,52(22):3240-3249
Novel cyclic olefin polymers (COPs) with excellent transparency and high glass‐transition temperature (Tg) synthesized from bulky norbornene derivative, exo‐1,4,4a,9,9a,10‐hexahydro‐9,10(1',2')‐benzeno‐l,4‐methanoanthracene (HBMN), and cis‐cyclooctene (COE) by ring‐opening metathesis copolymerization utilizing the “first‐generation Grubbs” catalyst, RuCl2(PCy3)2(CHPh), and subsequent hydrogenation was reported herein. To get amorphous copolymers, it was of great importance to control the feed ratios and the polymerization time for gradient copolymerization. All these copolymers showed very high Tgs (141.1–201.2 °C), which varied with the content of HBMN. The films of the gradient copolymers with only one Tg were highly transparent. On the contrary, all the block copolymers synthesized through sequential addition showed two thermal transition temperatures, Tg and melt temperature (Tm), and the films of these block copolymers were opaque. The mechanical performances of the COPs were also investigated. It is the first report that transparent COP could be prepared from bulky norbornene derivative and monocyclic olefin. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3240–3249 相似文献
15.
Munehisa Yasuniwa Takahiro Murakami Motonori Ushio 《Journal of Polymer Science.Polymer Physics》1999,37(17):2420-2429
Annealing of poly(butylene terephthalate) (PBT) was studied by differential scanning calorimetry (DSC) and small angle X‐ray scattering (SAXS) measurement. A PBT sample was annealed at a recrystallization temperature where recrystallization occurs with a maximum rate in the heating process of the sample. In the subsequent annealing steps, the annealed sample was annealed repeatedly at the recrystallization temperatures, and the stepwise annealing sample was obtained. Peak melting temperature (Tm) and sharpness of DSC peak of the stepwise annealing sample increased with the annealing step. A high melting‐temperature sample was obtained in a short time, and Tm increased up to 238.5°C which is higher than all the Tm values that appear in the literature. The long period calculated from SAXS curves of the stepwise annealing sample increased with the annealing step. The increase of crystallite size and perfection of the crystal in the stepwise annealing process is suggested. Annealing experiment indicated that T°m should be higher than about 235°C. Tm increased linearly with the annealing temperature of the final step in the stepwise annealing (Ta). The equilibrium melting temperature (T°m) for PBT was estimated to be 247°C by the application of a Hoffman–Weeks plot to the relation between Tm vs. Ta. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2420–2429, 1999 相似文献
16.
Rachele Pucciariello Vincenzo Villani Liberata Guadagno Vittoria Vittoria 《Journal of Polymer Science.Polymer Physics》2006,44(1):22-32
With differential scanning calorimetry, we have demonstrated a peculiar behavior under equilibrium conditions of neat poly(ε‐caprolactone) and its organophilic montmorillonite nanocomposites. In particular, in the determination of the equilibrium melting temperature by the extrapolation of the data of the melting temperature (Tm) versus the crystallization temperature (Tc), a bimodal trend has been observed. At the lower Tc's, the data of Tm follow a constant trend, whereas at the higher ones, the usual increasing trend has been obtained. Morphological observations by atomic force microscopy (AFM) have provided evidence of two different crystalline morphologies for the lower and higher Tc ranges. Moreover, AFM has shown that the thermal treatments strongly influence the clay dispersion in the polymer matrix. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 22–32, 2006 相似文献
17.
Minoru Nagata Sigeki Hizakae 《Journal of polymer science. Part A, Polymer chemistry》2003,41(19):2930-2938
4,4′‐(Adipoyldioxy)dicinnamic acid (CAC) was synthesized by a condensation of adipoyl chloride and 4‐hydroxycinnamic acid. The CAC6 copolymers were prepared by a high‐temperature solution polycondensation of a diacyl chloride of CAC, 1,6‐hexanediol (6), and poly(ethylene glycol) (PEG) in which the molecular weights of PEG are 1000, 2000, and 8300. Differential scanning calorimetric curves of the copolymers exhibited a glass‐transition temperature because of PEG moiety and two melting endotherms (Tm's); the one at the higher Tm was due to CAC6 moiety, and the other at the lower Tm was due to PEG moiety, suggesting that these copolymers are the block type. The incorporation of the PEG component decreased the tensile strength and initial modulus, but increased the elongation extremely. The enzymatic degradation was performed in phosphate buffer solution (pH 7.2) with Ps. cepacia lipase at 37 °C. The degradation rate of the copolymers increased significantly with an increasing content of PEG, which was correlated to the water absorption of the copolymers. All copolymers could undergo photocuring by ultraviolet (UV) light irradiation (λ > 280 nm) at ambient temperature, as examined by UV spectroscopy and solubility. The CAC6/E2000(50/50) film photocured for 3 min exhibited a good elastic property with a maximum tensile strength of 3.7 MPa and maximum elongation of 640%. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2930–2938, 2003 相似文献
18.
David R. Rohindra Masakazu Tanaka Keiichi Kuboyama Toshiaki Ougizawa 《Journal of Polymer Science.Polymer Physics》2009,47(18):1799-1808
The thermal behavior of three aromatic polyesters in a homologous series, poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate) (PTT), and poly(butylene terephthalate) (PBT) was studied under hydrostatic pressure up to 200 MPa by using a high pressure differential thermal analysis apparatus. Confining fluid high pressure dilatometer was used to establish the volume–temperature curves (in both solid and liquid regions) from which volume change on melting of these polyesters at atmospheric pressure was determined. Single endothermic peak was seen for PET and PTT, whereas PBT showed double peaks above 50 MPa. Pressure coefficient of melting temperature at atmospheric pressure (dTm/dp(0)), was obtained from the quadratic fit. The dTm/dp(0) for PTT was newly determined to be 0.445 KMPa?1, whereas for PET and PBT were 0.503 and 0.455 KMPa?1, respectively, comparable to reported values. The dTm/dp(0) exhibited the odd‐even behavior corresponding to odd and even number of methylene groups in the repeat unit. Enthalpy and entropy of fusion had the most influence on this coefficient. Entropy related to conformational and volume change were evaluated and the former was found to have a significant impact on the value of dTm/dp(0). © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1799–1808, 2009 相似文献
19.
Peng‐Fei Gou Wei‐Pu Zhu Ning Xu Zhi‐Quan Shen 《Journal of polymer science. Part A, Polymer chemistry》2008,46(19):6455-6465
Per‐2,3‐acetyl‐β‐cyclodextrin with seven primary hydroxyl groups was synthesized by selective modification and used as multifunctional initiator for the ring‐opening polymerization of ε‐caprolactone (CL). Well‐defined β‐cyclodextrin‐centered seven‐arm star poly(ε‐caprolactone)s (CDSPCLs) with narrow molecular weight distributions (≤1.15) have been successfully prepared in the presence of Sn(Oct)2 at 120 °C. The molecular weight of CDSPCLs was characterized by end group 1H NMR analyses and size‐exclusion chromatography (SEC), which could be well controlled by the molar ratio of the monomer to the initiator. Furthermore, amphiphilic seven‐arm star poly(ε‐caprolactone‐b‐ethylene glycol)s (CDSPCL‐b‐PEGs) were synthesized by the coupling reaction of CDSPCLs with carboxyl‐terminated mPEGs. 1H NMR and SEC analyses confirmed the expected star block structures. Differential scanning calorimetry analyses suggested that the melting temperature (Tm), the crystallization temperature (Tc), and the crystallinity degree (Xc) of CDSPCLs all increased with the increasing of the molecular weight, and were lower than that of the linear poly(ε‐caprolactone). As for CDSPCL‐b‐PEGs, the Tc and Tm of the PCL blocks were significantly influenced by the PEG segments in the copolymers. Moreover, these amphiphilic star block copolymers could self‐assemble into spherical micelles with the particle size ranging from 10 to 40 nm. Their micellization behaviors were characterized by dynamic light scattering and transmission electron microscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6455–6465, 2008 相似文献
20.
Photoreactive and degradable hyperbranched (HB) copolymers with various 3,4‐dihydroxycinnamic acid (DHCA) compositions, poly(ε‐caprolactone)‐co‐poly(3,4‐dihydroxycinnamic acid) (PCL‐co‐PDHCA), were obtained by thermal melt‐polycondensation of PCL and DHCA. The HB structures and the branching degree (BD) of the PCL‐co‐PDHCA copolymers were confirmed by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H NMR). The melting points (Tm) of the PCL‐co‐PDHCA copolymers changed depending on the PCL and DHCA composition by differential scanning calorimetry (DSC) measurements. Wide angle X‐ray diffraction (WXRD) analysis showed semi‐crystalline of the PCL and PCL‐co‐PDHCA polymers. The PCL‐co‐PDHCA copolymers showed good photoreactivities and fluorescent properties. Crosslinking of the cinnamoyl groups in the copolymers caused by UV irradiation affected the thermal stability and wettability slightly. Moreover, the hydrolysis experiments revealed that copolymers are facile degradable. 相似文献