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An efficient metal-free bimolecular homodifunctional ring-closure method was developed specifically for preparing well-defined cyclic polymers from unconjugated vinyl monomers. In this approach, well-defined homodifunctional linear polymers with azide terminals were prepared by using the reversible addition chain transfer polymerization/macromolecular design by interchange of xanthates (RAFT/MADIX)...
In this paper, the reversible crystal-crystal transition of poly(hexamethylene dithiocarbonate) (PHMDC) has been systematically studied. According to various experimental results, we confirm that the transition shares the common features with Brill transition that is widely observed in nylons. This transition is clearly associated with the reversible trans-gauche conformational transformation of the...
We have investigated phase behaviors of a series of polyphenylacetylene derivatives, poly[di(n-alkyl) ethynylterephthalates] (Pn, n is the number of carbon atoms of n-alkyl group, from 2 to 14), which are largely influenced by the length of n-alkyl tails on 2,5-position of the phenyl group. With short alkyl groups (n ≤ 6), Pns form columnar liquid crystalline (Col) phases due to the “jacketing effect”...
We studied the lamellar orientation of polyamide 6 (PA6) thin films with the thickness ranged from ∼5 μm to ∼20 nm on different solid substrates. The lamellar morphology was observed using atomic force microscopy and transmission electron microscopy, and the lamellar orientation was characterized using two-dimensional (2D) grazing incidence wide-angle X-ray diffraction (GI-WAXD) and selected area...
We investigated the solution crystallization behavior of a high molecular weight (MW) poly(ethylene oxide) (PEO) (PEO400k, MW of 4 × 10 5 g/mol) in ethanol with the concentrations ranged from dilute to semi-dilute (i.e., from 0.02 to 2 wt %). We followed the dissolving process of PEO400k using differential scanning colorimetry, small-angle X-ray scattering and solution light scattering. The...
Various methods were employed to study the thermal behaviors of a novel microbial polyhydroxyalkanoate (PHA) terpolyester, namely, poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (PHBVHHx) compared with poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx). PHBVHHx showed higher crystallization rate and degree of crystallinity. PHBVHHx exhibited also different multiple melting...
A series of vinyl monomers, 2, 5-bis [(4-methoxy benzyl) oxycarbonyl] styrene (MBCS); 2, 5-bis [(3, 5-dimethoxy benzyl) oxycarbonyl] styrene (DMBCS) and 2, 5-bis [(3, 4, 5-trimethoxy benzyl) oxycarbonyl] styrene (TMBCS) were synthesized and polymerized via free radical polymerization. The terminal groups of the semirigid side chain were systematically varied to investigate the effects of their numbers...
By focusing on a range of fractions of medium-chain-length polyhydroxyalkanoates (mcl-PHA), a more in-depth understanding of the thermal properties and the crystalline structure has been gained. Dual-mode melting was observed for all the fractionated samples. Further DSC analysis revealed that such phenomenon was due to the presence of two crystalline phases (phase I and phase II), forming at different...
A kind of novel amphiphilic triblock copolymers containing polyrotaxane (PR) as a central block was synthesized via the ATRP of poly(ethylene glycol) methyl ether methacrylate (PEGMA) initiated with polypseudorotaxanes made from a distal 2-bromopropionyl end-capped Pluronic F127 with a varying amount of β-CDs in the presence of Cu(I)Cl/N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) at 25°C in...
An optically active poly(phenylacetylene), poly{2-(R)-methyl-2-[4′-(tetradecyloxy)biphenyl-4-yloxy]propyl 4-ethynylbenzoate} (P1) is synthesized in a high yield with a high molecular weight (1.3×10 6 g/mol) by [Rh(nbd)Cl] 2 catalyst. The chemical structure of the polymer is characterized by IR and NMR spectroscopies with satisfactory analysis data. The polymer is soluble in many common...
The phase structures and transition behaviors of a series of side-chain liquid crystalline (LC) polymethacrylates based on p-methoxyazobenzene (PMnAzs, n=6, 8, 10, 12) were studied using differential scanning calorimetry, one- and two-dimensional (1D and 2D) wide-angle X-ray diffraction, and Fourier transform infrared spectroscopic experiments. The LC phase transition of PMnAz follows the sequence...
The co-aggregation process of a diblock copolymer poly(ethylene oxide)-block-polybutadiene (PEO-b-PB) and a homopolymer poly(acrylic acid) (PAA) in solutions was studied. The number-average molecular weights of both the PEO and PB blocks are 5100g/mol; the weight-average molecular weight of PAA is ∼2000g/mol. The co-aggregation was induced by adding a PB selective solvent (i.e., alkane or cycloalkane)...
Nonlinear optical response in various polyhydroxyalkanoates (PHAs) was investigated via second harmonic generation microscopy (SHGM). It was revealed that the second harmonic generation (SHG) efficiency depended on both the polymer chemical structure and the crystalline structure. Among the PHAs studied, the microbial polyesters, poly(R-3-hydroxybutyrate) (PHB) and poly(R-3-hydroxyvalerate) (PHV)...
Using atomic force microscopy (AFM) coupled with a hot stage, we studied the morphological evolution of superheated poly(ethylene oxide) (PEO) crystal monolayer on the mica surface. The PEO possesses a number average molecular weight (M n ) of 4250g/mol and a polydispersity of 1.03. The superheated monolayer was obtained when the entire periphery of a triply-folded chain crystal [IF(3)] was...
Three new β-diketone-containing styrenic monomers and their polymers were synthesized. The phenol and naphthol groups, and the electron-donating N,N-dimethylaniline groups were covalently attached to the β-diketone monomers at a designed position. The keto–enol tautomerism was characterized by 1 H, 13 C NMR and UV–vis absorption spectroscopy. It was found that the β-diketone monomers...
Crystallization and melting of a poly(ethylene oxide) (PEO) diblock copolymer containing a tablet-like block of poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PMPCS) in ultrathin films have been studied using atomic force microscopy (AFM) coupled with a hot stage. The PEO and PMPCS block possess the number-average molecular weights (M n ) of 5300 and 2100g/mol, respectively. The ultrathin...
Micropatterns of strap and farmland structures of polystyrene-block-poly(acrylic acid) (PS-b-PAA) copolymer were obtained by drying the micelle solutions. The drying process of the solution was monitored by dynamic optical microscopy (OM) with a digital video camera. The surface structure of the micelle aggregations was studied by OM, scanning electron microscopy and Alpha-Step 200 profiler system...
A low-molecular-weight poly(ethylene oxide) (PEO) fraction with a number-average molecular weight of 4250 g/mol was used to study the melting and recrystallization behaviors during heating. After complete crystallization at 46 °C, the PEO possessed almost exclusively once-folded chain [IF(n=1)] crystals and very few extended chain IF(n=0) crystals. Comparing differential scanning calorimetry heating...
Melting and crystallization of two types of polyhydroxyalkanoates (PHAs), poly(3-hydroxybutyrate) homopolymer (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) random copolymer (PHBHHx) were studied via in situ Fourier transform infrared spectroscopy (FTIR). The absorbance variances of the crystalline and the amorphous bands revealed that melting of PHB occurred at a narrow temperature range,...
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