Anionic Copolymerization of ε-Caprolactam with ω-Laurolactam

Polyamide 6/12 copolymers were prepared by employing two different initiation systems containing activator N-benzoyl-ε-caprolactam (BzCL) and initiator either sodium salt of ε-caprolactam (CLNa) or ε-caprolactam magnesium bromide (CLMgBr). Materials prepared by initiation with CLNa show one melting endotherm and are random copolymers. Materials prepared by initiation with CLMgBr show two melting endotherms and are probably composed from random copolymer and block copolymer containing blocks of random copolymer and blocks of copolymer with ε-caprolactam rich segments. The character of copolymers and fractionalized materials was evaluated by means of DSC and NMR.     

Homo-and Copolymerization of ε-Caprolactone and 2,2-Dimethyltrimethylene Carbonate by Rare Earth Initiators

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Polymerization of ε-Caprolactone and its Copolymerization with γ-Butyrolactone using Metal Complexes

Solution polymerization of ε-caprolactone (ε-CL) was performed using four different initiators namely: tin(II) octanoate (Sn(Oct)₂)/ethanolamine, aluminium Schiff's base complex-HAPENAlOⁱPr, lithium diisopropyl amide (LDA) and aluminium isopropoxide. The reaction conditions varied with the initiator used. LDA gave rise to the most rapid polymerization with the highest amount of cyclic species as detected by ¹³C NMR. However, no cyclic species were detected when HAPENAlOⁱPr was used as initiator. The tin(II) octanoate/ethanolamine system lead to an α,ω-dihydroxy-polycaprolactone (PCL). The copolymerization of ε-CL was then performed with the hard to oligomerize γ-butyrolactone using the four initiators. GPC (Gel Permeation Chromatography) analyses showed the formation of copolymers. The highest incorporation of polybutyrolactone (PBL) in the copolymer was obtained using HAPENAlOⁱPr as evidenced by ¹H NMR. ¹³C NMR indicated the presence of pseudoperiodic random copolymers with short blocks of PCL whose block length varied with initiator used. The longest and shortest block length were obtained using Sn(Oct)₂ and HAPENAlOⁱPr respectively as calculated from ¹³C NMR. The reactivity ratios were determined using the Finemann-Ross method at low conversion with HAPENAlOⁱPr as initiator. The values obtained, r_CL = 19.4 and r_BL = 0.11, confirmed the presence of long blocks of CL units in the copolymer.     

Homopolymerization and Copolymerization of Adipic Anhydride with ε-Caprolactone Catalyzed by Rare Earth Trisphenolate

The ring-opening polymerization of adipic anhydride and the ring-opening copolymerization of adipic anhydride with ε-caprolactone catalyzed by single component rare earth trisphenolate have been reported. The structure of the copolymer poly（CL-b-AA） has been characterized by SEC, ^1H NMR and DSC.     

Copolymerization of α-Methylstyrene and Styrene

In this paper, the effects of temperature from 60 °C to 80 °C and the molar ratios in monomer feed on the copolymerization of α-methylstyrene(AMS) and styrene(St) were studied. The resulting copolymers, designated as PAS, were characterized by FTIR, GPC, NMR and TGA. When the reaction temperature was below 75 °C, the molecular weights increased almost linearly as the evolution of the copolymerization. The phenomenon revealed that AMS could mediate the conventional free radical polymerization having some features of a controlled system. As the AMS/St = 50/50(molar) in feed, the overall fraction of the AMS unit incorporated into the copolymer was as high as 42 mol%, the monomer conversion could be more than 90 wt% and the molecular weights could reach as high as 4400. However, since the styrene is more reactive than AMS, the AMS fraction in copolymer increased with the overall monomer conversion. The 13C-NMR revealed the products were random copolymers which had triads, such as-AMS-AMS-AMS-,-St-AMS-AMS-(-AMS-AMS-St-) and-St-AMS-St-. TGA curves demonstrated that the degradation temperature of the resulting copolymers went down from about 356.9 °C(0 mol% AMS) to 250.2 °C(42 mol% AMS). This behavior demonstrated that there exist weak bonds in the AMScontaining sequences which could be used as potential free radical generators.     

Cationic Copolymerization with Depropagation. The Copolymerization of α-Methylstyrene and Styrene

ABSTRACT

To evaluate the existence of the depropagation reaction in the copolymerization of vinyl monomers, the cationic copolymerization of α-methylstyrene with styrene was studied. The copolymer composition exhibited an extensive dependency on the temperature of polymerization and the monomer concentration, this fact not being explained by the Mayo-Lewis equation. Treatment of the copolymerization in terms of the depropagation reaction led to an estimate of the monomer reactivity ratio and the equilibrium constant between the polymer and the monomer of α-methylstyrene. A comparison of the equilibrium constants thus obtained with those reported in the literature indicates that the magnitude of the equilibrium constants depends on the sequence length of α-methylstyrene units. By extrapolation to long sequence length, the equilibrium constants approach the values which are reported for high molecular weight poly(α-methylstyrene).     

Copolymerization and Properties of Multicomponent Crosslinked Hydrogels

A series of multicomponent hydrogels were prepared by the copolymerization of hydrophobic silicon-containing monomer 3-bis(trimethylsilyloxy) methylsilylpropyl glycerol methacrylate(Si MA) with the solvent-responsive monomers 2-hydroxyethyl methacrylate(HEMA) and N-vinyl pyrrolidone(NVP) and thermosensitive monomer N,N-dimethyl acrylamide(DMA). 2-Hydroxy-2-methyl phenyl acetone(D-1173) was chosen as UV initiator and five different dienes/triene monomers were selected as crosslinking agent in order to select the best crosslinker. The ethanol extraction experiments as well as the FTIR, DSC and TG results showed that the copolymerization was effective. The optical, permeability, and mechanical analysis results demonstrated that the obtained hydrogels were highly transparent with good oxygen permeability and mechanical properties. And the impact of crosslinker on the mechanical properties of the hydrogels was also discussed in detail. The basic results demonstrated that the obtained hydrogels had good stimuli-responsive effects to both p H value and solvent.     

L-Lactide Homopolymerization and Copolymerization with ε-Caprolactone by Tetrahydrosalen Stabilized Yttrium Borohydride Complex

L-lactide（LLA） homopolymerization and copolymerization with ε-caprolactone（CL） in toluene initiated by tetrahydrosalen-supported yttrium borohydride complex were systematically investigated. A possible mechanism of LLA homopolymerization was proposed according to the 1H-NMR result. In addition, PCL-b-PLLA copolymers were synthesized by sequential addition of monomers and their structure was characterized by GPC, 1H-NMR and 13C-NMR.     

Ring-Opening Copolymerization of 2,2-Dimethyltrimethylene Carbonate and ε-Caprolactone Using Rare Earth Aryloxides Substituted by Various Alkyl Groups

A variety of single component rare earth aryloxides substituted by various alkyl groups [Ln(OAr)₃] such as methyl, isopropyl, tert‐butyl have been surveyed in the ring‐opening copolymerization of 2,2‐dimethyltrimethylene carbonate (DTC) and ε‐caprolactone (ε‐CL). It was worthwhile to note that activity of the catalyst varied with both the ligands' structure and the number of alkyl groups on phenyl ring. The stronger ability of electron‐donation of alkyl groups on phenyl ring, and the more numbers of alkyl groups on phenyl ring, the higher catalytic activity. The experimental results show that lanthanum tris(2,4,6‐tri‐tert‐butylphenolate) [La(OTTBP)₃] exhibits highest activity in all lanthanum aryloxides. ¹H NMR spectral data of copolymer obtained showed that the polymerization mechanism is in agreement with the coordination insertion mechanism.     

Purification of γ-Benzyl and γ-Methyl L-Glutamate N-Carboxyanhydrides by Rephosgenation

Rephosgenation of N-carboxyanhydrides of γ-benzyl and y-methyl L-glutamates, vs multiple recrystallizations, is a very efficient method for obtaining highly purified N-carboxyanhydrides, from which very high MW (0.98-1.5 × 10⁶ Daltons) polymers can be derived.     

Cross-linking Copolymerization of Acrylic Acid and Multi-armed Cross-linkers

Polymer gels are of considerable interests in material science1-3. Many theoretical and experimental studies have been made on the cross-linking copolymerization4-6 of these systems. Recently, in situ interferometry is applied in studying this process7-9. As shown in Figure 1, the common two-armed cross-linkers will lead to defects in the network, while multi-armed cross-linkers will enhance the integrity of the network. This paper studies the cross-linkers influence on cross-linking and t…     

Flexible Gradient Poly(ether-ester) from the Copolymerization of Epoxides and ε-Caprolactone Mediated by a Hetero-bimetallic Complex

Copolymerization is a commonly employed method for optimizing the properties of polymer materials. Incorporating ether segments into polyesters main chain to obtain polyether-polyester copolymers is an effective strategy to realize the integration of multiple properties of polyester and polyether, and to develop more high-performance, multi-purpose polymer materials. Herein, the synthesis of poly(ether-ester)s is accessible by employing the biphenyl-linked heterodinuclear salen Cr-Al complex in the presence of PPNCl for the copolymerization of epoxides and ε-caprolactone(CL). Monitoring the copolymerization process reveals that catalyst 1 exhibited good performance for the copolymerization of epoxides and CL, affording copolymers with a gradient sequence structure. The dynamic thermomechanical analysis(DMA) study indicates the obtained poly(ether-ester)s possess enhanced flexibility compared with the block copolymers or blend of PPO and PCL homopolymers with the same ratio. This study provides a theoretical basis for the preparation of high-performance polymer materials.     

Ring-opening Copolymerization of ε-Caprolactone and δ-Valerolactone Catalyzed by a 2,6-Bis(amino)phenol Zinc Complex

In combination with methyllithium,a 2,6-bis(amino)phenol zinc complex 1 was used in the ring-opening polymerization ofδ-valerolactone in the absence or presence of benzyl alcohol and showed high efficiency,mainly producing cyclic and linear polyvalerolactones,respectively.On the basis of homopolymerization,the ring-opening copolymerization ofε-caprolactone andδ-valerolactone was investigated.The P(CL-co-VL)random copolymers,PCL-b-PVL and PVL-b-PCL diblock copolymers,were prepared by varying the feeding strategy(premixing or sequential feeding).The copolymer composition was adjusted by varying the feeding ratio of two monomers.The structure and thermal properties of obtained polymers were characterized by GPC,1 H-NMR,13 C-NMR,MALDI-TOF mass spectroscopy,and DSC,respectively.     

Electrospinning of polyesteramides based on ε-caprolactam and ε-caprolactone from solution

The paper is focused on the preparation of nanofiber layers of polyesteramides with various ratios of ε-caprolactam/ε-caprolactone structural units. We have studied the effect of the system parameters, i.e., the composition of the copolymer, its molar mass and the concentration of the solution on morphology of fiber layers being formed during the electrostatic wet spinning. The process parameters were constant during the processing. Morphology of the fiber layers is given by the composition of the copolymer, i.e., by its polarity, the content of the crystalline phase and thus its separation in the process of evaporating the solvent. Fibers with diameters ranging from 100 to 160 nm were obtained for polyesteramides containing 20 or 40 mol% lactone units during optimizing the system parameters, i.e., the concentration of the solution and molar mass of polyesteramide.     

Kinetics of Nonisothermal and Isothermal Crystallization of Metallocene Polyethylene

Thedevelopmentofmetallocenecatalystsundoubtedlyrepresentsarevolutioninthepolyolefinbusiness.MetallocenePE(MPE)coverspolyethyleneswhichareproducedbymetallocenecatalysttechnology.EXXONChemicalCo.developedanewmeta-llocenepolyethylene-EXCEED'"PEin1991.Nowmoreandmoreeffortsarespentonthisinterestingproject.Uniformmolecularstructureandnarrowmoleculardistribution,makeMPEbetterphysicalpropertiesthanthoseofconventionalPE,andalsomakeitlowmeltstrengthandbadprocessability.Sotherelationshipbetween…     

Synthesis and Characterization of ABBA Block Copolymer of Glycolide and ε-Caprolactone

A biodegradable ABBA block copolymer was synthesized via the ring-opening co-polymerization of ε-Scaprolactone (CL, B) and glycolide (A) by means of step polymerization in the presence of ethylene glycol as an initiator and stannous octanoate as a catalyst at 110 ℃ for 48 h. The molecular length of the PCL prepolymer(BB) could be adjusted by controlling the molar ratio of the ethylene glycol initiator to ε-caprolactone monomer. The structure and the composition of the block copolymer were determined by the weight ratio of the monomer glycolide (A) to PCL pre-polymer(BB). The block copolymers were characterized by ^1H NMR, GPC, DSC and X-ray. The results confirm the successful synthesis of an ABBA block copolymer.     

Synthesis and Characterization of ABBA Block Copolymer of Glycolide and ε-Caprolactone

A biodegradable ABBA block copolymer was synthesized via the ring-opening co-polymerization of ε-caprolactone(CL, B) and glycolide(A) by means of step polymerization in the presence of ethylene glycol as an initiator and stannous octanoate as a catalyst at 110 ℃ for 48 h. The molecular length of the PCL pre-polymer(BB) could be adjusted by controlling the molar ratio of the ethylene glycol initiator to ε-caprolactone monomer. The structure and the composition of the block copolymer were determined by the weight ratio of the monomer glycolide(A) to PCL pre-polymer(BB). The block copolymers were characterized by 1H NMR, GPC, DSC and X-ray. The results confirm the successful synthesis of an ABBA block copolymer.     

Reactivity Ratios for Microemulsion Copolymerization of N-butyl Maleimide and Styrene

The oil-in-water microemulsion containing N-butyl maleimide(NBMI, M1) and styrene(St, M2) was prepared. The complexation properties of NBMI and St in microemulsion were investigated by means of 1H-NMR. With the participation of charge-transfer complex(CTC), four reactivity ratios and the relative reactivity of free monomers and CTC were obtained. The result was compared with that measured by Mayo-Lewis method.     

Polymerization of lactams. 99 Preparation of polyesteramides by the anionic copolymerization of ε-caprolactam and ε-caprolactone

Polyesteramides derived from the cyclic monomers ε-caprolactam and ε-caprolactone have been synthesized by the anionic polymerization and characterized. ε-Caprolactam magnesium bromide was employed as unique initiator giving high yield of copolymer across the whole range of monomer concentrations at 150 °C. Owing to a variation of the content of ester and amide component in polyesteramide backbone a large variety of materials having diverse physico-chemical and mechanical properties have been prepared. Materials prepared were examined for mechanical characteristic. Thermal properties were characterized using DSC, temperature modulated DSC, Hi-Res^TM TGA and DMA. Viscosity measurements were employed for molecular characterization.