Organostibine mediated controlled/living random copolymerization of styrene and methyl methacrylate

The first example of organostibine mediated controlled/living random copolymerization of styrene(St) and methyl methacrylate(MMA) was achieved by heating a solution of St/MMA/organostibine mediator at 100 °C or St/MMA/organostibine mediator/AIBN with various monomer feed ratios at 60 °C.The addition of AIBN significantly decreased the reaction temperature and enhanced the rate of copolymerization.The structure of poly(St-co-MMA) was verified by 1H NMR.The reactivity ratios at 60 °C were determined by the extended Kelen-Tüds method to be YSt = 0.40 and YMMA = 0.44.The ln([M]0/[M]) increased linearly with increasing reaction time.The number-average molecular weights of poly(St-co-MMA) increased linearly with conversion.Poly(St-co-MMA) with expected number-average molecular weight and low polydispersity index was formed.The living characteristic was further confirmed by chain-extension of poly(St-co-MMA) to form poly(St-co-MMA)-b-PMMA.

Rapid synthesis of biodegradable poly(epsilon-caprolactone-co-p-dioxanone) random copolymers under microwave irradiation

Biodegradable poly(epsilon-caprolactone-co-p-dioxanone)(PCDO) random copolymers have been synthesized by ring-opening polymerization of epsilon-caprolactone(CL) and p-dioxanone(PDO) under microwave irradiation.The effects of irradiation time and different CL/PDO molar feed ratios on the microwave-assisted ring-opening polymerization(MROP) of PCDO have been discussed.The resultant products were characterized by ~1H NMR,GPC and DSC.It was found that the polymerization was completed within 20 min at 140℃.In th...

Influence ofβ-nucleating Compound Agents on the Mechanical Properties and Crystallization Behavior of Polypropylene Random Copolymer

A novel polypropylene random(PPR)composite materials with optimized properties was developed by addingβ-nucleating compound agents(rare earth complex WBG-2 and aryl amide derivative TMB-5)and ternary compound modifier(TPE/WBG-2/CaCO_(3)).The effects of differentβ-nucleating agents and ternary compound modifier on the mechanical properties and crystallization behavior of PPR were analyzed.The results show that,compared with pure PPR materials,both WBG-2 and TMB-5 could significantly improve the impact strength of PPR.The crystallization temperature of PPR increased with the addition ofβ-nucleating agent.The modified PPR prepared with ternary compound modifier showed the most excellent comprehensive properties.

Sequence design in terpolymerization ofε-caprolactone,CO_(2) and cyclohexane oxide:Random ester-carbonate distributions lead to large-span tunability

It is of great interest to make a degradable material widely tailorable to replace petroleum-derived products among diverse applications.Here,we report the construction of a new multi-purpose degradable material for the first time via a simple ternary copolymerization system comprisingε-caprolactone(ε-CL),cyclohexane oxide(CHO)and CO_(2).Under low pressure of 1 bar∼5 bar,the ring-opening polymerization(ROP)ofε-CL and ring-opening copolymerization(ROCOP)of CO_(2) and CHO can simultaneously proceed.The carbonate units are randomly distributed on the polymer chain.These random terpolymers have controllable molar mass(10-106 kDa)and compositions(4-33 mol%CO_(2)).And the obtained materials show large-span tunability from tough plastic to elastomer and even adhesive.

Synthesis and Characterization of Poly(L-lactide-co-ε-caprolactone) Copolymers

A series of random and block poly（ L-lactide-co-e-caprolactone ） （ PCLA ） copolymers whh different composition are prepared using stannous octaoate as catalyst.The effects of the amount of initiator on the intrinsic viscosity have been investigated. The structure of the PCLA copolymers is characterized by means of nuclear magnetic resonance（ NMR ）, Fourier transform infrared spectrum （ FTIR ）, differential scanning calorimetry （ DSC ） and X- ray diffraction （ XRD ） methods. It is shown that the synthesis condition and the composition of copolymers obrious influence on the structure of PCLA copolymers. Hydrolytic degradation of the copolymers in a PBS solution of pH 7.4 at 37.0℃ shows that the copolymers of different composhions degrade at different rates.

Effect of Long Chain Branching on the Rheological Behavior,Crystallization and Mechanical Properties of Polypropylene Random Copolymer

Long chain branched polypropylene random copolymers （LCB-PPRs） were prepared via reactive extrusion with the addition of dicumyl peroxide （DCP） and various amounts of 1,6-hexanediol diacrylate （HDDA） into PPR. Fourier transform infrared spectrometer （FTIR） was applied to confirm the existence of branching and（ investigate the grafting degree for the modified PPRs. Melt flow index （MFI） and oscillatory shear rheological properties including complex viscosity, storage modulus, loss tangent and the Cole-Cole plots were studied to differentiate the LCB-PPRs from linear PPR. Differential scanning calorimetry （DSC） and polarized light microscopy （PLM） were used to study the melting and crystallization behavior and the spherulite morphology, respectively. Qualitative and quantitative analyses of rheological curves demonstrated the existence of LCB. The effect of the LCB on crystalline morphology, crystallization behavior and molecular mobility, and, thereby, the mechanical properties were studied and analyzed. Due to the entanglements between molecular chains and the nucleating effect of LCB, LCB-PPRs showed higher crystallization temperature and crystallinity, higher crystallization rate, more uniformly dispersed and much smaller crystallite compared with virgin PPR, thus giving rise to significantly improve impact strength. Moreover, the LCB-PPRs exhibited the improved yield strength. The mobility of the molecular chain segments, as demonstrated by dynamic mechanical analysis （DMA）, was improved for the modified PPRs, which also contributed to the improvement of their mechanical properties.

Mechanism of Polymorph Selection during Crystallization of Random Butene-1/Ethylene Copolymer

Starting from an initial sample of butene-1/ethylene copolymer with stable form I＇, we examined the nucleation of different crystalline polymorphs （here metastable form II and stable form I＇） at different isothermal crystallization temperatures after being melted at different melt temperature （Tmelt）. When Tmelt was just above the melting temperature （Tm） of the crystallites, self-seeding took place. There, residue crystallites served as nuclei leading to the crystallization of the same crystalline phase. When Tmelt was a few degrees above the Tin, self-seeding was disabled due to complete melting of the initial crystals. Upon crystallization, the selection of the different polymorphs in this random copolymer was found to depend on an interplay between the domain size of segregated long crystallizable sequences and the size and energy barrier of the critical nucleus of the respective crystalline forms. Our results provide a clear understanding of the polymorphs selection during crystallization of a random copolymer as well as homo-polymers under confinement.

COMBINED EFFECT OF MODIFIED ZEOLITE 13X AND β-NUCLEATING AGENT ON IMPROVING β-CRYSTAL CONTENT AND TOUGHENING POLYPROPYLENE RANDOM COPOLYMER

Although addition of β-nucleating agent directly into homo-polypropylene （PPH） is a useful method to improve ,β-crystal content and toughen PPH, polypropylene random copolymer （PPR） makes this method powerless due to its random structure and low crystallinity. In this study, the β-nucleated PPR with high β-crystal content was prepared by a novel high effective β-nucleating system which consists of β-nucleation agent （TMB-5） and modified zeolite 13X （M13X）. It was found that M13X and TMB-5 had a synergistic influence on improving β-crystal content and toughening PPR. The content of β-crystal in PPR/M13X/TMB-5 was significantly larger than the sum of that in PPR/M13X and PPR/TMB-5. Besides, fracture behavior, phase morphology and relaxation of matrix chain segments were also investigated. The results showed that M13X and TMB-5 improved the mobility of amorphous chain segments at low temperature and contributed to much energy dissipation. This work provides a powerful method to modify PPR.

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

Rare earth tris(2,6-di-tert-butyl-4-methylphenolate) [Ln-(OAr)3, Ln = La, Nd, Dy, Y] alone has been developed to initiate polymerization of e-caprolactone (CL) and random copolymerization of CL with 2, 2-dimethyltrimethylene carbonate (DTC). The structures of polymers were analyzed by GPC, ER and NMR methods. Their crystal and thermal properties were discussed in terms of DSC. The initiating efficiencies were mainly affected by the size of rare earth metal in the sequence of La(OAr)3 > Nd(OAr)3 ～ Y(OAr)3 > Dy(OAr)3. La-(OAr)3 exhibited rather high activity to prepare PCL with a molecular weight of 2.15 × 105 and Ma/Ma of 2.27. The composition of random copolymer can be quantitatively controlled either by reaction time or by feed ratio of monomer.

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.

SYNTHESIS AND CHARACTERIZATION OF RANDOM OR GRADIENT BUTADIENE-p-METHYLSTYRENE COPOLYMERS VIA ANIONIC POLYMERIZATION

Copolymers of 1,3-butadiene and p-methylstyrene （p-MS） were synthesized via anionic polymerization. A benzophenone-potassium complex was added to tune the reactivity ratio of the two monomers, leading to random and gradient composition alonglthe copolymer chain. The overall composition and microstructure could be controlled and well characterized by GPC and H-NMR. The p-MS was distributed from gradient to random with increasing the content of the benzophenone-potassium complex, and the 1,2-microstrucmre in the polybutadiene sequence increased at the same time. The hydrogenation of the copolymer of 1,3-butadiene and p-MS resulted in the corresponding saturated copolymer with well- defined structure and narrow molecular weight distribution.

Enhanced Ultraviolet Resistance of Polypropylene Random Copolymer Filled by ZnO-supported Mesoporous Zeolite

To enhance the ultraviolet resistance of ZnO based polymer materials, ZnO-supported mesoporous zeolite（M-ZnO） was prepared and characterized by atomic absorption spectroscopy and scanning electron microscopy. The ultraviolet resistance, crystallization behavior and melting characteristics of ZnO and M-ZnO filled PPR composites were compared by FTIR spectra and differential scanning calorimetry. The ultraviolet resistance of M-ZnO filled PPR composites is higher than that of ZnO filled PPR composites, indicating higher ultraviolet resistance of M-ZnO than that of ZnO. The crystallization temperatures of mesoporous zeolite filled PPR were higher than those of M-ZnO and decreased with increasing UV-irradiation time. But the crystallization temperatures of M-ZnO filled PPR composites were not influenced by UV-irradiation time. The ZnO supported on the surface of zeolite is effective in enhancing the ultraviolet resistance of ZnO based polymer materials.

Micelle-crosslinked hydrogels with stretchable,self-healing,and selectively adhesive properties:Random copolymers work as dynamic yet self-sorting domains

The design of crosslinking domains is a vital factor to create functional hydrogels with controlled physical,mechanical,and adhesive properties.This paper demonstrates versatile synthetic systems of micelle-crosslinked hydrogels with highly stretchable,self-healing,and selectively adhesive properties.For this,methacrylate-bearing random copolymer micelles are designed as physical and covalent crosslink domains via the self-assembly of amphiphilic random copolymers carrying hydrophilic poly(ethylene glycol)(PEG),hydrophobic butyl or dodecyl groups,and methacrylate-terminal PEG in water.The size,aggregation number,and pendant methacrylate number of the micelles are controlled by the composition and degree of polymerization.Hydrogels are efficiently obtained from the free radical polymerization of hydrophilic monomers such as PEG acrylate and acrylamide in the presence of the micelle crosslinkers in water.Owing to the dynamic yet selective chain exchange properties of the micelle domains,the hydrogels are highly stretchable up to over 1000%and show self-healing and selectively adhesive properties.The self-healing of hydrogels is promoted upon heating due to the fast chain exchange of the micelle domains,whereas hydrogels consisting of micelles with different alkyl groups are never adhesive because of their self-sorting properties.

Enhanced Mechanics in Injection Molded Isotactic Polypropylene/Polypropylene Random Copolymer Blends via Introducing Network-like Crystal Structure

The crystallization behavior, rheological behavior, mechanical properties and microstructures of injection molded isotactic polypropylene （iPP）, polypropylene random copolymer （co-PP） and iPP/co-PP blends were investigated. Differential scanning calorimetry （DSC） and dynamic rheological analysis illustrated that iPP and co-PP were compatible in the blends and co-PP uniformly dispersed in the/PP phase. Polarizing optical microscope （POM） was adopted to observe the crystal size and morphology evolution. The results of mechanical properties and scanning electron microscopy （SEM） indicated that the crystal size of iPP in iPP/co-PP blends （10 wt% co-PP ＋ 90 wt% iPP and 30 wt% co-PP ＋ 70 wt% iPP） radically decreased after the incorporation of co-PP. During crystallization, the molecular chain segments of co-PP could penetrate iPP spherulites and form a network-like crystalline structure. The network-like crystal structure could effectively transmit stress and consume more energy to overcome intermolecular forces to resist stretching. In this way, the strength would improve to a certain degree. The impact fracture mechanism of iPP/co-PP blends is quasi ductile fracture by multiple crazes. Our work discovered that the blends containing 10 wt% and 30 wt% ofco-PP exhibited prominent toughness and reinforcement.

TIME AND POLING HISTORY DEPENDENT ENERGY STORAGE AND DISCHARGE BEHAVIORS IN POLY(VINYLIDENE FLUORIDE-CO-HEXAFLUOROPROPYLENE) RANDOM COPOLYMERS

We studied cycle time （0.01-10 s with triangular input waves） and poling history （continuous versus fresh poling） dependent electric energy storage and discharge behaviors in poly（vinylidene fluoride-co-hexafluoropropylene） [P（VDF- HFP）] films using the electric displacement -- the electric field （D-E） hysteresis loop measurements. Since the permanent dipoles in PVDF are orientational in nature, it is generally considered that both charging and discharging processes should be time and poling history dependent. Intriguingly, our experimental results showed that the charging process depended heavily on the cycle time and the prior poling history, and thus the D-E hysteresis loops had different shapes accordingly. However, the discharged energy density did not change no matter how the D-E loop shape varied due to different measurements. This experimental result could be explained in terms of reversible and irreversible polarizations. The reversible polarization could be charged and discharged fairly quickly （〈 5 ms for each process）, while the irreversible polarization depended heavily on the poling time and the prior poling history. This study suggests that it is only meaningful to compare the discharged energy density for PVDF and its copolymer films when different cycle times and poling histories are used.

Morphology and Properties of PP In-reactor Alloys Prepared with a MgCl2/TiCl4/Diisobutyl Phthalate/Phosphate Tris-methylphenyl Ester Catalyst System

A series of polypropylene（PP）/poly（ethylene-co-propylene） in-reactor alloys with different ethylene contents was prepared through a two-stage polymerization process using a MgCl2/TiCl4/diisobutyl phthalate/phosphate tris-methylphenyl ester catalyst system. The ethylene content, particle shape, fractured surface, and glass-transition temperature（Tg） of the obtained PP in-reactor alloys were characterized by means of nuclear magnetic resonance, scanning electron microscopy（SEM）, and dynamic mechamcal analysis（DMA）. The ethylene content of the PP alloys increased from 2.34% to 26.69% when the propylene/ethylene feed ratio was increased from 66/34 to 54/46（molar ratio）. Morevoer, the increment in ethylene content increased the notched Izod impact strength of the resulting PP alloys. The impact strength of the PP alloy with an ethylene content of 26.69% was 55.8 kJ/m^2, which is 12.7 times that of isotactic polypropylene. The results of DMA and SEM analysis reveal that ethylene-propylene random copolymer（EPR） in the PP alloy has a low Tg of ca. -50℃ and a high interface compatibility with the PP matrix. The excellent impact performance of the PP alloy can be attributed to the uniform dispersal of EPR in the alloy particles and PP matrix.

Preparation and Properties of Super-hydrophobic Surface by Fluorinated Copolymers

1 Rusults Fig.1 Surface morphologies of the PMMA-PFAEA copolymer filmsa-e, Random copolymer, a-e, synthesized by micro emulsion polymerization,a)b), MMA:FAEA=2:1, c) d), MMA:FAEA=5:1; e) synthesized by solution polymerization, MMA:FAEA=7:3; f) Block copolymer, synthesized by RAFT polymerization, MMA:FAEA=4:1, all solution concentration 1×10-2g/mL Super-hydrophobic surfaces have attracted significant attention recently, and various preparing methods have been reported. Besides these preparing methods, s...

Distinctive Polymorphism-like Isodimorphism in Poly(propylene succinate-ran-propylene fumarate)

Co-crystallization of different monomeric units fundamentally contributes to the versatile and tunable performance of random copolymers.At present,the crystallization manners of random binary copolymers have been divided into three categories:isomorphism,isodimorphism and comonomer exclusion.Each category,however,has its own advantages and disadvantages.Therefore,it is challenging to design and prepare random copolymer sharing the advantages of isomorphism and isodimorphism through a new co-crystallization manner beyond the ones already exist.On the basis of previous study on poly(alkylene succinate-ran-alkylene fumarate)whose co-crystallization can be extensively and finely regulated by simply varying the chemical structure of alkylene,random copolymers of poly(propylene succinate-ranpropylene fumarate)(PPSF)are synthesized using 1,3-propanediol as the diol source.The thermal properties and crystal structure of PPSF are investigated,and,intriguingly,it is proved that PPSF is an isodimorphism system while displays similar composition-dependent thermal properties and crystallinity as isomorphism.That is,PPSF exhibits a novel co-crystallization behavior that has rarely been discovered,which would combine the advantages of both isomorphism and isodimorphism.Consequently,PPSF could be termed as a new-type,special compositiondependent polymorphism.Besides,the altering of PPS-like to PPF-like crystal structure of PPSF when changing chain composition has been proved to originate from the shift of dominant inter-segment interaction from van der Waals forces to strong hydrogen-bonding interaction.This work enriches the co-crystallization manner of random copolymers,leading to more diverse performance design of polymer materials.