Alternating Copolymerization of Propylene Oxide/Alkylene Oxide and Carbon Dioxide: Tuning Thermal Properties of Polycarbonates

Current research efforts in the field of poly(propylene carbonate) prepared from carbon dioxide and propylene oxide are reviewed. Interest in the polymer has been revived in light of the current discussion on sustainability and biodegradability. The progress in understanding and increasing the activity of heterogeneous zinc catalysts is steadily increasing, but without a quantum leap. The microstructure, the properties of the melt, and the solid material are given. The material property profile can be expanded through the synthesis of terpolymers based on propylene oxide, carbon dioxide and other epoxides, lactones or anhydrides etc. with the same catalyst; or the preparation of poly(propylene carbonate) blends with biodegradable or biocompatible components like calcium carbonate, wood flour, fibers, or other biodegradable polymers.

To improve the thermal and mechanical properties of poly(propylene carbonate) (PPC), the copolymerization of CO2 with PO was successfully carried out in the presence of a third monomer, 4,4′-diphenylmethane diisocyanate (MDI) using supported multi-component zinc dicarboxylate as catalyst. Chemical structure, the molecular weight, as well as thermal and mechanical properties of the resulting new copolymers were fully investigated. The experimental results show that the yield increases with increasing MDI feed content from 0 to 2 wt.%. The introduction of MDI leads to an increase in the molecular weight of PPC with light crosslinking. When the MDI feed content is lower than 3 wt.%, the PPC copolymers have number average molecular weight (Mn) ranging from 153 K to 424 K g/mol and molecular weight distribution (MWD) values ranging from 1.71 to 2.79. The resulting PPC copolymers show higher glass transition temperature (Tg) and decomposition temperature compared with poly(propylene carbonate) (PPC) without MDI. Considering the gel content of the resulting copolymers, the optimized MDI feed content should be smaller than 1.5 wt.% based on PO content. The introduction of small amount of MDI provides a very effective way to improve the mechanical properties and thermal stabilities of PPC due to the increase in its molecular weight.

Using supported multi-component zinc dicarboxylate catalyst, poly(1,2-propylene carbonate-co-1,2-cyclohexylene carbonate) (PPCHC) was successfully synthesized from carbon dioxide (CO2) with propylene oxide (PO) and cyclohexene oxide (CHO). The conversion of epoxides dramatically increased up to 89.7% (yield: 384.2 g of polymer per g of Zn) with increasing reaction temperature from 60°C to 80°C. The optimized reaction temperature is 80°C. The chemical structure, the molecular weight, as well as thermal and mechanical properties of the resulting terpolymers were investigated extensively. When CHO feed content (mol%) is lower than 10%, the PPCHC terpolymers have number average molecular weight (Mn) ranging from 102 × 103 to 202 × 103 and molecular weight distribution (MWD) values ranging from 2.8 to 3.5. In contrast to poly(propylene carbonate) (PPC), the introduction of small amount of CHO leads to increase in the glass transition temperature from 38.0°C to 42.6°C. Similarly, the mechanical strength of the synthesized terpolymer is greatly enhanced due to the incorporation of CHO. These improvements in mechanical and thermal properties are of importance for the practical application of PPC.

The homogeneous dinuclear zinc catalyst going back to the work of Williams et al. is to date the most active catalyst for the copolymerisation of cyclohexene oxide and CO(2) at one atmosphere of carbon dioxide. However, this catalyst shows no copolymer formation in the copolymerisation reaction of propylene oxide and carbon dioxide, instead only cyclic carbonate is found. This behaviour is known for many zinc-based catalysts, although the reasons are still unidentified. Within our studies, we focus on the parameters that are responsible for this typical behaviour. A deactivation of the catalyst due to a reaction with propylene oxide turns out to be negligible. Furthermore, the catalyst still shows poly(cyclohexene carbonate) formation in the presence of cyclic propylene carbonate, but the catalyst activity is dramatically reduced. In terpolymerisation reactions of CO(2) with different ratios of cyclohexene oxide to propylene oxide, no incorporation of propylene oxide can be detected, which can only be explained by a very fast back-biting reaction. Kinetic investigations indicate a complex reaction network, which can be manifested by theoretical investigations. DFT calculations show that the ring strains of both epoxides are comparable and the kinetic barriers for the chain propagation even favour the poly(propylene carbonate) over the poly(cyclohexene carbonate) formation. Therefore, the crucial step in the copolymerisation of propylene oxide and carbon dioxide is the back-biting reaction in the case of the studied zinc catalyst. The depolymerisation is several orders of magnitude faster for poly(propylene carbonate) than for poly(cyclohexene carbonate).

Conventional polymer materials from fossil fuels feature many unresolved questions regarding disposing and future resource availability. To substitute some of the established plastics with bio-based and biodegradable alternatives, new materials have to be developed and researched. The aliphatic biodegradable polyester poly(butylene succinate) offers good material properties and the perspective to be partially bio-based in the future. Poly(propylene carbonate) is an amorphous co-polymer of propylene oxide and carbon dioxide. The incorporation of carbon dioxide in the polymer offers a great way to reduce the excess CO2 levels in the atmosphere and at the same time to add a bio-based component to the plastic. By melt blending and injection molding these two materials, partially bio-based, potentially biodegradable blends are generated. The blends’ mechanical, thermal and morphological properties are studied, using DSC, DMA, TMA, SEM, and FTIR analysis as well as tests regarding impact, flexural and tensile properties. Furthermore, the shrinkage of PPC, PBS and their blends is examined. It was found that blending of these two materials, without any additives or fillers, is not very promising, as almost all mechanical and thermal properties are decreased compared to the neat PBS. However, shrinkage of PPC can be eliminated when added into a PBS matrix and low contents of PPC might offer a possibility to increase the impact toughness of PBS.

Comparative in vitro degradation of surface-eroding poly(alkylene carbonate)s

ABSTRACTTo determine the thermal characteristics of linear and crosslinked polyimides (PIs), BTDA, ODPA, and 6FDA were used to synthesize polyimides. Thermal degradation temperature and glass transition temperature of the resulting PIs were measured using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). To measure the change in modulus and coefficient of thermal expansion (CTE) depending on dianhydride structure, a dynamic mechanical analyzer (DMA) and thermo‐mechanical analyzer (TMA) were used. The thermal degradation and glass transition temperature properties of linear PIs varied according to whether the linear chain adopted a bulky or flexible structure. Dynamic modulus and thermal expansion values of linear polyimides also showed good agreement with the TGA and DSC results. As we expected, linear polyimide with bulky 6FDA groups showed better thermal behavior than the flexible polyimides. Crosslinked polyimide nadic end‐capped (norbornene) with a bulky dianhydride group had a lower thermal degradation temperature and higher CTE than flexible BTDA and ODPA polyimides. Our results indicate that the mobility of the dianhydride group affects the thermal behaviors of linear and crosslinked polyimides in different ways. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41412.

Synthesis, characterization and hydrolysis of an aliphatic polycarbonate by terpolymerization of carbon dioxide, propylene oxide and maleic anhydride

To enhance the thermal and mechanical properties of poly(propylene carbonate) (PPC), the terpolymers were synthesized from carbon dioxide, propylene oxide, and a third monomer, [(2‐naphthyloxy)methyl]oxirane (NMO) using supported zinc glutarate as catalyst. The structure of these terpolymers was confirmed by 1H NMR spectroscopy. The catalytic activity, molecular weight, carbonate unit content, as well as thermal and mechanical properties were investigated extensively. The experimental results showed that the catalytic activity, molecular weight, and carbonate unit content decreased with the incorporation of NMO. DSC measurements indicated that the introduction of NMO increased the glass transition temperature from 38 to 42°C. TGA tests revealed that the thermal decomposition temperature (Tg−5%) of the synthesized terpolymer increased significantly, being 34°C higher than that of pure PPC. Accordingly, the mechanical properties proved also to be enhanced greatly as evidenced by tensile tests. These thermal and mechanical improvements are of importance for the practical process and application of PPC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

This paper deals with fabrication and characterization of unique polyphenylene ether/polystyrene/nylon-6/glass composites. Compounding of ternary blends with glass fibres was performed using twin screw co-rotating extruder. Test specimens were fabricated by compression moulding and injection moulding. Effect of maleic anhydride, fibre type (chopped and long), fibre content (30 wt. % and 40 wt. %) and fabrication method (compression moulding and injection moulding) on mechanical and thermal properties was studied. Maleic anhydride negatively influenced mechanical and thermal properties. Composites with 40 wt. % chopped fibres showed superior mechanical strength and those with 30 wt. % long fibres showed superior thermal properties, tensile and flexural moduli. Injection moulded specimens exhibited superior mechanical and thermal properties. The composites were studied for moisture content, density, melt flow index, glass transition temperature, thermal degradation temperature and mechanical properties. Interfacial strength was examined using scanning electron microscopy.

온실가스 가운데 하나인 이산화탄소를 활용하기 위한 연구의 일환으로 프로필렌옥사이드와 사이클로헥신옥사이드, 그리고 이산화탄소를 원료로 하고 zinc glutarate를 촉매로 하여 여러가지 조성의 삼원공중합체가 합성되었다. 이고분자는 FT-IR, <TEX>$^1H$</TEX>-NMR, DSC을 이용하여 분석되었고, 이들의 유리전이온도는 poly(alkylene carbonate)의 두성분의 질량비와 일정한 관계를 가지며 Fox식과 비교적 일치함을 확인하였다. In order to use carbon dioxide, one of the green house gases, terpolymers have been synthesized from propylene oxide, cyclohexene oxide, and carbon dioxide with zinc glutarate as catalyst. The polymers have been investigated with FT-IR, <TEX>$^1H$</TEX>-NMR, DSC. The glass transition temperatures of terpolymers are dependendent upon mass ratio of the poly(alkylene carbonate by Fox equation.

Essential work of fracture analysis for starch filled poly(propylene carbonate) composites

1. The solubility of C9–C10 aromatic hydrocarbons in propylene and chloropropylene carbonates was established at temperatures from 0 to 100°C. 2. It was found that propylene and chloropropylene carbonates can be successfully used for the extraction of aromatic hydrocarbons. Moreover, propylene carbonate is substantially more effective than chloropropylene carbonate; therefore its use is preferable for the extraction of C9–C10 aromatic hydrocarbons. 3. The expediency of conducting the extraction of C9–C10 aromatic hydrocarbons with propylene carbonate at temperatures of 20–50°C and with chloropropylene carbonate at 75–100°C was demonstrated.

Synthesis, stereocomplex crystallization, homo-crystallization, and thermal properties and degradation of enantiomeric aromatic poly(lactic acid)s, poly(mandelic acid)s

Wool powder: An efficient additive to improve mechanical and thermal properties of poly(propylene carbonate)